A two-dimensional simulation to predict the electrical behavior of carbon nanotube/polymer composites

Dosimetry characteristics of Epoxy/MWCNT nanocomposite in the field of gamma-rays: Effect of thickness

Polymer-carbon nanostructures have been used as gamma-ray dosimeters. The thickness of the sensitive volume material plays an important role in the determination of the dosimetry response. In this work, the thickness effect of a real-time dosimeter based on the Epoxy/Multi-walled carbon nanotube (MWCNT) nanocomposite was investigated. The amount of electrical percolation threshold (EPT) for Epoxy/MWCNT nanocomposite was initially simulated using the finite element method. Then, the 0.1 MWCNT wt% nanocomposite was fabricated using a solution method with three thicknesses of 1, 2, and 3 mm. FESEM images demonstrated a good dispersion state of the inclusions into the Epoxy matrix. The samples were irradiated by gamma-rays of Co-60 source over the dose rates of 25-166 mGy/min. In addition, dosimetric characteristics were performed, including linearity, bias-polarity, angular dependence, energy dependence, field size, and repeatability. Results revealed that with increasing the thickness, the dosimetry response was enhanced remarkably.

Gamma irradiation induced surface modification of (PVC/HDPE)/ZnO nanocomposite for enhancing the oil removal and conductivity using COMSOL multiphysics

Blend nanocomposite film was prepared by loadings of irradiated ZnO in ratios of (5 wt%) inside the PVC/HDPE matrix using a hot-melt extruder technique. The physical and chemical properties of the irradiated and unirradiated ZnO samples are compared. The Vis-UV spectrum of ZnO shows an absorption peak at a wavelength of 373 nm that was slightly red-shifted to 375 nm for an irradiated sample of ZnO at a dose of 25 kGy due to the defect of crystal structure by the oxygen vacancy during gamma irradiations. This growth of the defect site leads to a decrease in energy gaps from 3.8 to 2.08 eV. AC conductivity of ZnO sample increased after the gamma irradiation process (25 kGy). The (PVC/HDPE)/ZnO nanocomposites were re-irradiated with γ rays at 25 kGy in the presence of four different media (silicon oil, sodium silicate, paraffin wax and water). FTIR and XRD were performed to monitor the changes in chemical composition. The new peak at 1723 cm^-1 attributed to C=O groups was observed in irradiated (PVC/HDPE)ZnO samples at only sodium silicate and water media. This process induced new function groups on the surface of the (PVC/HDPE)/ZnO blend sample. This work aims to develop (PVC/HDPE)ZnO for oil/water separation. The highest oil adsorption capability was observed in samples functionalized by C=O groups based on the different tested oils. The results suggest that the surface characterization of the (PVC/HDPE)/ZnO can be modified to enhance the oil adsorption potential. Further, the gamma irradiation dose significantly enhanced the AC conductivity compared to the unirradiated sample. According to COMSOL Multiphysics, the irradiated sample (PVC/HDPE)ZnO in water shows perfect uniform electric field distribution in medium voltage cables (22.000 V).

Enhanced Ionic Polymer-Metal Composites with Nanocomposite Electrodes for Restoring Eyelid Movement of Patients with Ptosis

The present study aims to use enhanced ionic polymer-metal composites (IPMC) as an artificial muscle (a soft-active actuator) to restore eyelid movement of patients with ptosis. The previous eyelid movement mechanisms contained drawbacks, specifically in the lower eyelid. We used finite element analysis (FEA) to find the optimal mechanism among two different models (A and B). In addition to common electrodes of IPMC (gold and platinum), the bovine serum albumin (BSA) and microcrystalline cellulose (MCC) polymers, with optimal weight percentages of carbon nanotube (CNT) nanofiller, were also utilized as non-metallic electrodes to improve the efficiency of the IPMC actuator. In both models, IPMC with nanocomposite electrodes had higher efficiency as compared to the metallic electrodes. In model A, which moved eyelids indirectly, IPMC with MCC-CNT electrode generated a higher force (25.4%) and less stress (5.9 times) as compared to IPMC with BSA-CNT electrode. However, the use of model A (even with IPMCs) with nanocomposite electrodes can have limitations such as possible malposition issues in the eyelids (especially lower). IPMC with MCC-CNT nanocomposite electrode under model B, which moved eyelids directly, was the most efficient option to restore eyelid movement. It led to higher displacements and lower mechanical stress damage as compared to the BSA-CNT. This finding may provide surgeons with valuable data to open a window in the treatment of patients with ptosis.

Computational prediction of electrical percolation threshold in polymer/graphene-based nanocomposites with finite element method

In this research work, a two-dimensional model to predict the electrical percolation threshold (EPT) of the polymer/graphene-based nanocomposites in different concentrations of the randomly dispersed inclusions in various polymer matrices is introduced using the finite element method (FEM). The predicted EPT values were validated by other experimental results for different nanocomposites. Results showed that the electrical conductivity of different nanocomposites is significantly related to the percentage weight of the reinforcing phase in the polymer matrix. Furthermore, the addition of graphene-based nano-fillers in the polymer matrix caused a decrease in the tunneling distance in nanocomposites.

Computational prediction of electrical percolation threshold in polymer/graphene-based nanocomposites with finite element method

In this research work, a two-dimensional model to predict the electrical percolation threshold (EPT) of the polymer/graphene-based nanocomposites in different concentrations of the randomly dispersed inclusions in various polymer matrices is introduced using the finite element method (FEM). The predicted EPT values were validated by other experimental results for different nanocomposites. Results showed that the electrical conductivity of different nanocomposites is significantly related to the percentage weight of the reinforcing phase in the polymer matrix. Furthermore, the addition of graphene-based nano-fillers in the polymer matrix caused a decrease in the tunneling distance in nanocomposites.

Evaluation of dosimetric characteristics of a ternary nanocomposite based on High Density Polyethylene/Bismuth Oxide/Graphene Oxide for gamma-rays

This research aims to investigate a ternary nanocomposite based on High Density Polyethylene/ Bismuth Oxide/Graphene Oxide (HDPE/Bi2O3/GO) at various concentrations. Solution method was used to fabricate the samples. FESEM-EDX mapping, AFM, TEM, XRD, XPS, FTIR, and TGA/DTG analyses were carried out on the samples. XRD analysis demonstrated a semi-crystalline behavior for the samples. TEM analysis exhibited a cauliflower-like structure of the material. The sample was irradiated by gamma-rays of 60Co source over the dose rate of 30–254 mGy/min and the electric current was measured as the response of the real-time dosimeter. Thus, various dosimetric characteristics were performed, namely linearity, angular dependence, energy dependence, bias-polarity, field size, and repeatability of the data. Results showed that response of the dosimeter was linear in the range of the investigated dose rate. The sensitivity of the 60 wt% Bi2O3 sample was measured as 3.4 nC·mGy−1. The angular response variation was 20% for normal beam incidence. The response of the dosimeter to assess the energy dependency was obtained as 2.2% at the radiation field of the 137Cs and 60Co beams. The dosimeter response was dependent on the bias-polarity, with maximum discrepancy of 11.1%. The dosimetry response was highly dependent upon the radiation field size. The repeatability of the dosimeter response was measured with standard deviation less than 1%. As well, the dosimeter response during the one-hour irradiation was stable with a standard deviation of 0.66%. Results showed that considering some correction factors, this material can be used for dosimetry of gamma-rays at the therapy level.

Evaluation of dosimetric characteristics of a ternary nanocomposite based on High Density Polyethylene/Bismuth Oxide/Graphene Oxide for gamma-rays

This research aims to investigate a ternary nanocomposite based on High Density Polyethylene/ Bismuth Oxide/Graphene Oxide (HDPE/Bi₂O₃/GO) at various concentrations. Solution method was used to fabricate the samples. FESEM-EDX mapping, AFM, TEM, XRD, XPS, FTIR, and TGA/DTG analyses were carried out on the samples. XRD analysis demonstrated a semi-crystalline behavior for the samples. TEM analysis exhibited a cauliflower-like structure of the material. The sample was irradiated by gamma-rays of ⁶⁰Co source over the dose rate of 30-254 mGy/min and the electric current was measured as the response of the real-time dosimeter. Thus, various dosimetric characteristics were performed, namely linearity, angular dependence, energy dependence, bias-polarity, field size, and repeatability of the data. Results showed that response of the dosimeter was linear in the range of the investigated dose rate. The sensitivity of the 60 wt% Bi₂O₃ sample was measured as 3.4 nC·mGy^-1. The angular response variation was 20% for normal beam incidence. The response of the dosimeter to assess the energy dependency was obtained as 2.2% at the radiation field of the ¹³⁷Cs and ⁶⁰Co beams. The dosimeter response was dependent on the bias-polarity, with maximum discrepancy of 11.1%. The dosimetry response was highly dependent upon the radiation field size. The repeatability of the dosimeter response was measured with standard deviation less than 1%. As well, the dosimeter response during the one-hour irradiation was stable with a standard deviation of 0.66%. Results showed that considering some correction factors, this material can be used for dosimetry of gamma-rays at the therapy level.

Introducing a novel beta-ray sensor based on polycarbonate/bismuth oxide nanocomposite

In this research, for the first time, the polycarbonate/bismuth oxide (PC-Bi₂O₃) composite was studied as a beta-ray sensor using a pure beta-emitter ⁹⁰Sr source. Firstly, the range and stopping power of the electrons in the composite at various loadings of 0, 10, 20, 30, 40, and 50 wt% were calculated using the ESTAR program. Results of simulation demonstrated that the concentration of the heavy metal oxide particles into the polymer matrix played an important role in evaluating the range and stopping power of the electrons in the composite. Secondly, at the experimental phase, the pure Polycarbonate and 50 wt% PC-Bi₂O₃ nanocomposite with dimensions of 4 × 4 × 0.1 cm³ were prepared and irradiated by ⁹⁰Sr. Also, current-voltage (I-V) plot exhibited linear response ranging from 100 to 1000 V at the fixed source-to-surface distance (SSD). Then the amount of electric current as the sensor response was measured in various dose rates at the fixed voltage of 400 V for the pure Polycarbonate and 50 wt% PC-Bi₂O₃ nanocomposite using an electrometer, in which results showed that the sensitivities were found as 20.3, and 33.3 nC mSv^-1 cm^-3, respectively. This study showed that this composite could serve as a novel beta-ray sensor.

Introducing a novel beta-ray sensor based on polycarbonate/bismuth oxide nanocomposite

In this research, for the first time, the polycarbonate/bismuth oxide (PC–Bi2O3) composite was studied as a beta-ray sensor using a pure beta-emitter 90Sr source. Firstly, the range and stopping power of the electrons in the composite at various loadings of 0, 10, 20, 30, 40, and 50 wt% were calculated using the ESTAR program. Results of simulation demonstrated that the concentration of the heavy metal oxide particles into the polymer matrix played an important role in evaluating the range and stopping power of the electrons in the composite. Secondly, at the experimental phase, the pure Polycarbonate and 50 wt% PC–Bi2O3 nanocomposite with dimensions of 4 × 4 × 0.1 cm3 were prepared and irradiated by 90Sr. Also, current–voltage (I–V) plot exhibited linear response ranging from 100 to 1000 V at the fixed source‐to‐surface distance (SSD). Then the amount of electric current as the sensor response was measured in various dose rates at the fixed voltage of 400 V for the pure Polycarbonate and 50 wt% PC–Bi2O3 nanocomposite using an electrometer, in which results showed that the sensitivities were found as 20.3, and 33.3 nC mSv−1 cm−3, respectively. This study showed that this composite could serve as a novel beta-ray sensor.

Evaluation of gamma radiation response of electrolyte, MKP and MKT capacitors in various frequencies

In this experimental work, the effect of gamma irradiation on the capacitance and impedance of some commercial capacitors namely electrolytic, MKP, and MKT capacitors in different radiation doses up to 120 kGy and a wide range of frequencies between 42 Hz and 5 MHz were studied. Results showed that the capacitances of the electrolytic capacitors exhibited a linear decrease by increasing the radiation dose and frequencies, which can be used for high dosimetry purposes, but non-ceramic capacitors as MKP and MKT showed much higher radiation resistance, particularly for the frequencies less than ~1 MHz.