Production of flexible nanocomposite membranes for x-ray detectors

Flexible membranes of poly(vinyl alcohol) (PVA) polymer and CuO nanoparticles for x-ray detection applications are reported in this work. PVA represents a polymer matrix for nanoparticles, and its flexibility and electrical conductivity are enhanced by addition of glycerol (GL) plasticizer. Nanoparticles of an average size of 6.3∓2.4nm are produced by a solvothermal method and added to the PVA + GL solution with different concentrations. The flexible membranes are fabricated by solution casting on glass substrates. The effect of blending of PVA + GL with nanoparticles on different characteristics of the membranes including the flexibility as well as the melting, glass transition, and degradation temperatures are tested by differential scanning calorimetry, thermal gravimetric analysis, as well as both Raman and Fourier-transform infrared spectroscopy. Electrical impedance tests reveal that both dc resistance and activation energy decrease with increasing temperature as well as nanoparticle concentration. The produced membranes reveal electrical response to x-ray due to the presence of CuO nanoparticles, and this response rises with x-ray generator voltage. The results presented in this study specify that the produced membranes are easy to produce with low cost, thus, they represent potential candidates for practical applications including x-ray detection

A review on lithium recovery using electrochemical capturing systems

Resource recovery from natural reserves is appealing and Li extraction from different brines is in the forefront. Li extraction by membranes is reviewed in the literature much more than electrochemical processes. However, a very recent review thoroughly discussed Li recovery by electrochemically switchable ion exchange (ESIX). This paper reviews Li recovery by both charge transfer processes, namely electrodialysis (ED), and electro-sorption processes, namely capacitive deionization (CDI). It also reviews ESIX with a focus on performance matrices and includes comments on the technology readiness of each separation technique. These processes exhibit promising perspectives on the separation and recovery of Li both selectively and non-selectively from simulated brine solutions and Li salt solutions. Readers are provided with guidelines to choose between the processes, depending on the applied voltage, current density, specific energy consumption and purity of recovered Li. Most electrochemical lithium capturing systems (ELiCSs) have been tested at the lab scale. Therefore, future research should be directed toward pilot-scale development and parameter optimization. Furthermore, we urge the ELiCSs research community to report information in a standard form that allows meaningful comparisons and insights into the systems.This publication was made possible by NPRP grant # [NPRP12S-0227-190166] from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved are solely the responsibility of the authors. Open Access funding provided by the Qatar National Library

Fluence Correction Factor for Various Materials in Clinical Proton Dosimetry.

The fluence correction factor, which accounts for the loss of primary protons and the production of secondary particles due to different non-elastic nuclear interactions at water equivalent depths in different phantom materials compared to water is an important parameter for the dose conversion in clinical proton dosimetry between any phantom material and water. Non-elastic nuclear interactions introduce uncertainties in the standard absorbed dose-to-water in radiotherapy. This thesis is part of an ongoing project at the UK National Physical Laboratory (NPL) focussed on the development of graphite calorimeters for proton dosimetry. The fluence correction factor was investigated to give accurate dose conversions from dose-to-graphite in a graphite phantom to dose-to-water in a water phantom. The fluence correction factors at water equivalent depths have been studied for various dosimetric materials including A-150 tissue equivalent, polymethyl methacrylate (PMMA), aluminium and copper with respect to water and with respect to graphite. The water equivalence of materials such as Plastic Water (PW), Plastic Water Diagnostic Therapy (PWDT) and solid water (WT1) phantoms was evaluated using a 60 MeV proton beam at the Clatterbridge Centre for Oncology. Plastic-water phantoms are widely used in radiotherapy as a substitute for water, in particular for non-reference dosimetry. However, while they are usually made ‘water equivalent’ for a particular beam type, they are not universally water equivalent due to their different elemental composition and associated different proton interaction cross sections (compared to water). Numerous studies of the water equivalence of plastic-water phantoms have been reported for photon and electron beams, but none with clinical proton beams. In the latter, non-elastic nuclear interactions take place which could potentially influence the water equivalence. This thesis evaluates the fluence correction factor at equivalent depths for proton energies of 60 MeV and 200 MeV, with respect to both water and graphite. This work was performed using analytical model calculations (which incorporate the ICRU-49 (1993) stopping power data tables and ICRU-63 (2000) for the total nuclear interaction cross sections); Monte Carlo simulations using the FLUKA 2008. 3 code; and also experimental work at the Clatterbridge Centre for Oncology (CCO) 60 MeV with both modulated and unmodulated proton beams. The analytical calculations for primary protons indicate an increase in the fluence correction at both low and high energies compared to the Monte Carlo simulations. When the secondary charged particle were considered in the calculation, the fluence correction factor with respect to water was in general close to the unity for graphite, A-150, PMMA, aluminium and plastic-water materials in 60 MeV mono-energetic beam. For proton energies of 200 MeV, the fluence correction was found to increase to a the order of a few percent. The experimental finding for modulated and un-modulated 60 MeV protons showed that the fluence correction factor with respect to water is close to unity for graphite and PWDT with an uncertainty of 0. 2% at 1o. The derived fluence correction with respect to graphite was also close to the unity for A-150 and plastic-water materials, however, it was found to increase with depth to approximately 4% and 6% for aluminium and copper respectively (in modulated beam). In general, the experimental results for modulated and unmodulated 60 MeV proton beams show good agreement with the Monte Carlo simulations for modulated and un-modulated beams, yielding small fluence corrections, within the statistical uncertainty. For 200 MeV protons, the Monte Carlo simulations showed that the correction with respect to water increased with penetration depth giving values of up to 4% for graphite and 1. 5% for A-150, PMMA, aluminium, copper and plastic-water materials. The fluence correction with respect to graphite was found to vary with penetration depth and hence it can be concluded that fluence correction factors need to be applied to ensure accurate dosimetry for all of the materials used in the current work with a 200 MeV proton beam

Fluence Correction Factor for Various Materials in Clinical Proton Dosimetry.

The fluence correction factor, which accounts for the loss of primary protons and the production of secondary particles due to different non-elastic nuclear interactions at water equivalent depths in different phantom materials compared to water is an important parameter for the dose conversion in clinical proton dosimetry between any phantom material and water. Non-elastic nuclear interactions introduce uncertainties in the standard absorbed dose-to-water in radiotherapy. This thesis is part of an ongoing project at the UK National Physical Laboratory (NPL) focussed on the development of graphite calorimeters for proton dosimetry. The fluence correction factor was investigated to give accurate dose conversions from dose-to-graphite in a graphite phantom to dose-to-water in a water phantom. The fluence correction factors at water equivalent depths have been studied for various dosimetric materials including A-150 tissue equivalent, polymethyl methacrylate (PMMA), aluminium and copper with respect to water and with respect to graphite. The water equivalence of materials such as Plastic Water (PW), Plastic Water Diagnostic Therapy (PWDT) and solid water (WT1) phantoms was evaluated using a 60 MeV proton beam at the Clatterbridge Centre for Oncology. Plastic-water phantoms are widely used in radiotherapy as a substitute for water, in particular for non-reference dosimetry. However, while they are usually made ‘water equivalent’ for a particular beam type, they are not universally water equivalent due to their different elemental composition and associated different proton interaction cross sections (compared to water). Numerous studies of the water equivalence of plastic-water phantoms have been reported for photon and electron beams, but none with clinical proton beams. In the latter, non-elastic nuclear interactions take place which could potentially influence the water equivalence. This thesis evaluates the fluence correction factor at equivalent depths for proton energies of 60 MeV and 200 MeV, with respect to both water and graphite. This work was performed using analytical model calculations (which incorporate the ICRU-49 (1993) stopping power data tables and ICRU-63 (2000) for the total nuclear interaction cross sections); Monte Carlo simulations using the FLUKA 2008. 3 code; and also experimental work at the Clatterbridge Centre for Oncology (CCO) 60 MeV with both modulated and unmodulated proton beams. The analytical calculations for primary protons indicate an increase in the fluence correction at both low and high energies compared to the Monte Carlo simulations. When the secondary charged particle were considered in the calculation, the fluence correction factor with respect to water was in general close to the unity for graphite, A-150, PMMA, aluminium and plastic-water materials in 60 MeV mono-energetic beam. For proton energies of 200 MeV, the fluence correction was found to increase to a the order of a few percent. The experimental finding for modulated and un-modulated 60 MeV protons showed that the fluence correction factor with respect to water is close to unity for graphite and PWDT with an uncertainty of 0. 2% at 1o. The derived fluence correction with respect to graphite was also close to the unity for A-150 and plastic-water materials, however, it was found to increase with depth to approximately 4% and 6% for aluminium and copper respectively (in modulated beam). In general, the experimental results for modulated and unmodulated 60 MeV proton beams show good agreement with the Monte Carlo simulations for modulated and un-modulated beams, yielding small fluence corrections, within the statistical uncertainty. For 200 MeV protons, the Monte Carlo simulations showed that the correction with respect to water increased with penetration depth giving values of up to 4% for graphite and 1. 5% for A-150, PMMA, aluminium, copper and plastic-water materials. The fluence correction with respect to graphite was found to vary with penetration depth and hence it can be concluded that fluence correction factors need to be applied to ensure accurate dosimetry for all of the materials used in the current work with a 200 MeV proton beam

Effect of Voltage Level on the Performance of Silicone Rubber in the Inclined Plane Tracking and Erosion Test

This paper investigates the effect of the test voltage level on the performance of silicone rubber in inclined plane tracking and erosion test. Silicone rubber composites, filled with either alumina tri-hydrate or ground silica to 30 wt% or 50 wt%, are tested in inclined plane tracking and erosion test under 2.5 kV, 3.5 kV, and 4.5 kV. The degradation patterns of the tested silicone rubber surfaces are found dependent on the test voltage level during the inclined plane tracking and erosion test, as the dry-band arcing on silicone rubber tends to form tracks under relatively mild test voltages and deep erosion under the critical test voltage. These findings confirm the importance of employing the critical voltage while evaluating the erosion resistance of silicone rubber in the inclined plane tracking and erosion test. In addition, the critical test voltage of silicone rubber is found dependent on the amount of filler added to the composite.A. El-Hag, M. K. Hassan, A. Abdala, and L. Al-Sulaiti acknowledge that this work was made possible by NPRP grant 12S-0227-190168 from Qatar National Research Fund (a member of Qatar Foundation) and the Qatar University International collaboration grant no. IRCC-2020-010. The statements made herein are solely the responsibility of the authors: A. El-Hag, M. K. Hassan, A. Abdala, and L. Al-Sulaiti.Scopu

Self-Healing Silicones for Outdoor High Voltage Insulation: Mechanism, Applications and Measurements

This paper discusses the state of the art in the application of self-healing silicone-based materials for outdoor high-voltage insulation. Both the dynamic behavior of the dimethyl side groups of silicone rubber and the diffusion of a bulk siloxane to maintain low surface energy are respectively reported as intrinsic mechanisms responsible for the self-healing of silicone rubber. Localization, temporality, mobility, and the type of synthesis are the aspects defining the efficiency of the self-healing ability of silicone rubber. In addition, the deterioration of the self-healing ability with filler loaded into silicone rubber insulation housing composites is discussed. Taking the self-healing property into consideration among the other properties of silicone rubber insulators, such as tracking and erosion resistance, can be a useful design practice at the material development stage. Hydrophobicity retention, recovery, and transfer measurements are discussed as useful indicators of the self-healing ability of silicone rubber. Nevertheless, there remains a need to standardize them as design tests at the material development stage. The paper is intended to shed the light on the hydrophobicity recovery, a key material design parameter in the development of silicone rubber outdoor insulating composites, similar to the tracking and erosion resistance

Self-Healing Silicones for Outdoor High Voltage Insulation: Mechanism, Applications and Measurements

This paper discusses the state of the art in the application of self-healing silicone-based materials for outdoor high-voltage insulation. Both the dynamic behavior of the dimethyl side groups of silicone rubber and the diffusion of a bulk siloxane to maintain low surface energy are respectively reported as intrinsic mechanisms responsible for the self-healing of silicone rubber. Localization, temporality, mobility, and the type of synthesis are the aspects defining the efficiency of the self-healing ability of silicone rubber. In addition, the deterioration of the self-healing ability with filler loaded into silicone rubber insulation housing composites is discussed. Taking the self-healing property into consideration among the other properties of silicone rubber insulators, such as tracking and erosion resistance, can be a useful design practice at the material development stage. Hydrophobicity retention, recovery, and transfer measurements are discussed as useful indicators of the self-healing ability of silicone rubber. Nevertheless, there remains a need to standardize them as design tests at the material development stage. The paper is intended to shed the light on the hydrophobicity recovery, a key material design parameter in the development of silicone rubber outdoor insulating composites, similar to the tracking and erosion resistance.Acknowledgments: F. Kamand, B. Mehmood, A. El-Hag, M. Hassan, L. Al-Sulaiti, and A. Abdala acknowledge that this work was made possible by NPRP grant 12S-0227-190168 from Qatar National Research Fund (a member of Qatar Foundation) and the Qatar University International collaboration grant #: IRCC-2020-010. The statements made herein are solely the responsibility of the authors: F. Kamand, B. Mehmood, A. El-Hag, M. Hassan, L. Al-Sulaiti, and A. Abdala.Scopu

Pt-Based Nanostructures for Electrochemical Oxidation of CO: Unveiling the Effect of Shapes and Electrolytes

Direct alcohol fuel cells are deemed as green and sustainable energy resources; however, CO-poisoning of Pt-based catalysts is a critical barrier to their commercialization. Thus, investigation of the electrochemical CO oxidation activity (COOxid) of Pt-based catalyst over pH ranges as a function of Pt-shape is necessary and is not yet reported. Herein, porous Pt nanodendrites (Pt NDs) were synthesized via the ultrasonic irradiation method, and its CO oxidation performance was benchmarked in different electrolytes relative to 1-D Pt chains nanostructure (Pt NCs) and commercial Pt/C catalyst under the same condition. This is a trial to confirm the effect of the size and shape of Pt as well as the pH of electrolytes on the COOxid. The COOxid activity and durability of Pt NDs are substantially superior to Pt NCs and Pt/C in HClO4, KOH, and NaHCO3 electrolytes, respectively, owing to the porous branched structure with a high surface area, which maximizes Pt utilization. Notably, the COOxid performance of Pt NPs in HClO4 is higher than that in NaHCO3, and KOH under the same reaction conditions. This study may open the way for understanding the COOxid activities of Pt-based catalysts and avoiding CO-poisoning in fuel cells