Study of Ultrasonic Dispersion of Graphene Nanoplatelets

Ultrasonication Influence on the Morphological Characteristics of Graphene Nanoplatelet Nanocomposites and Their Electrical and Electromagnetic Interference Shielding Behavior

Graphene nanoplatelets (GNPs)/epoxy composites have been fabricated via gravity molding. The electrical and thermal properties of the composites have been studied with variable GNP type (C300, C500, and C750, whose surface areas are ~300, 500, and 750 m2/g, respectively), GNP loading (5, 10, 12, and 15 wt.%), and dispersion time via ultrasonication (0, 30, 60, and 120 min). By increasing the time of sonication of the GNP into the epoxy matrix, the electrical conductivity decreases, which is an effect of GNP fragmentation. The best results were observed with 10-12% loading and a higher surface area (C750), as they provide higher electrical conductivity, thereby preserving thermal conductivity. The influence of sonication over electrical conductivity was further analyzed via the study of the composite morphology by means of Raman spectroscopy and X-ray diffraction (XRD), providing information about the aspect ratio of GNPs. Moreover, electromagnetic shielding (EMI) has been studied up to 4 GHz. Composites with C750 and 120 min ultrasonication show the best performance in EMI shielding, influenced by their higher electrical conductivity.

Graphene as a rational interface for enhanced adsorption of microcystin-LR from water

Cyanotoxins such as microcystin-LR (MC-LR) represent a global environmental threat to ecosystems and drinking water supplies. The study investigated the direct use of graphene as a rational interface for removal of MC-LR via interactions with the aromatic ring of the ADDA1 chain of MC-LR and the sp2 hybridized carbon network of graphene. Intra-particle diffusion model fit indicated the high mesoporosity of graphene provided significant enhancements to both adsorption capacities and kinetics when benchmarked against microporous granular activated carbon (GAC). Graphene showed superior MC-LR adsorption capacity of 75.4 mg/g (Freundlich model) compared to 0.982 mg/g (Langmuir model) for GAC. Sorption kinetic studies showed graphene adsorbs 99% of MC-LR in 30 min, compared to zero removal for GAC after 24 hr using the same MC-LR concentration. Density functional theory (DFT), calculations showed that postulated π-based interactions align well with the NMR-based experimental work used to probe primary interactions between graphene and MC-LR adduct. This study proved that π-interactions between the aromatic ring on MC-LR and graphene sp2 orbitals are a dominant interaction. With rapid kinetics and adsorption capacities much higher than GAC, it is anticipated that graphene will offer a novel molecular approach for removal of toxins and emerging contaminants with aromatic systems.

A Novel Approach to Water Softening Based on Graphene Oxide-Activated Open Cell Foams

This work focuses on exploring a new configuration for the reduction of water hardness based on the surface modification of polyurethane (PU) open cell foams by the deposition of thin graphene oxide (GO) washcoat layers. GO was deposited by the dip–squeeze coating procedure and consolidated by thermal treatment. The final washcoat load was controlled by performing consecutive depositions, after three of which, a GO inventory up to 27 wt% was obtained onto PU foams of 60 pores per inch (PPI). The GO-coated PU foams were assembled into a filter, and the performance of the system was tested by continuously feeding water with hardness in the 190–270 mgCa2+,eq·L−1 range. Remarkable results were demonstrated in terms of total adsorbing capacity, which was evaluated by measuring the outlet total hardness by titration and exhibited values up to 63 mgCa2+,eq·gGO−1 at a specific filtered water volume of 650 mLH2O·gGO−1, outperforming the actual state-of-the-art adsorbing capacity of similar GO-based materials.

Ultrasonication effects on graphene composites in neural cell cultures

Spinal cord injuries and neurodegenerative diseases, including Parkinson’s, Alzheimer’s, and traumatic brain injuries, remain challenging to treat. Nowadays, neural stem cell therapies excite high expectations within academia. The increasing demand for innovative solutions in regenerative medicine has drawn considerable attention to graphene materials. Due to unique properties, carbon materials are increasingly used as cellular scaffolds. They provide a biological microenvironment supporting cell adhesion and proliferation. The topography and mechanical properties of the graphene culture surface influence the forces exerted by the cells on their extracellular matrix. Which consequently affects the cell proliferation and differentiation. As a result, material properties such as stiffness, elasticity and mechanical strength play an important role in stem cells’ growth and life. The ink unification process is crucial while the layer homogeneity is essential for obtaining suitable surface for specific cell growth. Different ink unification processes were tested to achieve appropriate layer homogeneity and resistivity to successfully applied the GNPs layers in neural cell electrostimulation. The GNP coatings were then used to electrostimulate mouse NE-4C neural stem cells. In this study, the authors investigated how the stimulation voltage amplitude’s value affects cell behaviour, particularly the number of cells. Sinusoidal alternating current was used for stimulation. Three different values of stimulation voltage amplitude were investigated: 5, 10, and 15 V. It was noticed that a lower stimulation voltage amplitude had the most favourable effect on the stem cell count.

Characterization 0.1 wt.% Nanomaterial/Photopolymer Composites with Poor Nanomaterial Dispersion: Viscosity, Cure Depth and Dielectric Properties

Notably, 3D printing techniques such as digital light processing (DLP) have the potential for the cost-effective and flexible production of polymer-based piezoelectric composites. To improve their properties, conductive nanomaterials can be added to the photopolymer to increase their dielectric properties. In this study, the microstructure, viscosity, cure depth, and dielectric properties of ultraviolet (UV) light curable 0.1 wt.% nanomaterial/photopolymer composites are investigated. The composites with multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), and carbon black (CB) are pre-dispersed in different solvents (acetone, isopropyl alcohol, and ethanol) before adding photopolymer and continuing dispersion. For all prepared suspensions, a reduction in viscosity is observed, which is favorable for 3D printing. In contrast, the addition of 0.1 wt.% nanomaterials, even with poor dispersion, leads to curing depth reduction up to 90% compared to pristine photopolymer, where the nanomaterial dispersion is identified as a contributing factor. The formulation of MWCNTs dispersed in ethanol is found to be the most promising for increasing the dielectric properties. The post-curing of all composites leads to charge immobility, resulting in decreased relative permittivity.

Ultrasonically Processed WSe2 Nanosheets Blended Bulk Heterojunction Active Layer for High-Performance Polymer Solar Cells and X-ray Detectors

Two-dimensional (2D) tungsten diselenide (WSe2) has attracted considerable attention in the field of photovoltaic devices owing to its excellent structure and photoelectric properties, such as ordered 2D network structure, high electrical conductivity, and high mobility. For this test, we firstly prepared different sizes (NS1-NS3) of WSe2 nanosheets (NSs) through the ultrasonication method and characterized their structures using the field emission scanning electron microscope (FE-SEM), Raman spectroscopy, and X-ray powder diffraction. Moreover, we investigated the photovoltaic performance of polymer solar cells based on 5,7-Bis(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione(PBDB-T):(6,6)-phenyl-C71 butyric acid methyl ester (PCBM) with different WSe2 NSs as the active layer. The fabricated PBDB-T:PCBM active layer with the addition of NS2 WSe2 NSs (1.5 wt%) exhibited an improved power conversion efficiency (PCE) of 9.2%, which is higher than the pure and NS1 and NS3 WSe2 blended active layer-encompassing devices. The improved PCE is attributed to the synergic enhancement of exciton dissociation and an improvement in the charge mobility through the modified active layer for polymer solar cells. Furthermore, the highest sensitivity of 2.97 mA/Gy·cm2 was achieved for the NS2 WSe2 NSs blended active layer detected by X-ray exposure over the pure polymer, and with the NS1 and NS2 WSe2 blended active layer. These results led to the use of transition metal dichalcogenide materials in polymer solar cells and X-ray detectors.

Ultrasonication an intensifying tool for preparation of stable nanofluids and study the time influence on distinct properties of graphene nanofluids - A systematic overview

Optimum ultrasonication time will lead to the better performance for heat transfer in addition to preparation methods and thermal properties of the nanofluids. Nano particles are dispersed in base fluids like water (water-based fluids), glycols (glycol base fluids) &oils at different mass or volume fraction by using different preparation techniques. Significant preparation technique can enhance the stability, effects various parameters & thermo-physical properties of fluids. Agglomeration of the dispersed nano particles will lead to declined thermal performance, thermal conductivity, and viscosity. For better dispersion and breaking down the clusters, Ultrasonication method is the highly influential approach. Sonication hour is unique for different nano fluids depending on their response to several considerations. In this review, systematic investigations showing effect on various physical and thermal properties based on ultrasonication/ sonication time are illustrated. In this analysis it is found that increased power or time of ideal sonication increases the dispersion, leading to higher stable fluids, decreased particle size, higher thermal conductivity, and lower viscosity values. Employing the ultrasonic probe is substantially more effective than ultrasonic bath devices. Low ultrasonication power and time provides best outcome. Various sonication time periods by various research are summarized with respect to the different thermophysical properties. This is first review explaining sonication period influence on thermophysical properties of graphene nanofluids.

Metal-insert technique for polypropylene composite bipolar plate manufacturing

A single cell of direct methanol fuel cell (DMFC) typically delivers an electrical potential between 0.5 and 1 V; thus DMFCs are assembled in parallel to meet power demands (1–5 kW). Bipolar plates (BPs) are the primary components connecting a single cell to the adjacent cells so that they provide optimum electrical conductivity. The objective of this research is to reduce the volume resistance of BPs made from a polypropylene/carbon composite by utilizing a metal insert technique. A major obstacle when it comes to molding composite plates inserted by a thin metal sheet is the delamination of material layers after the cooling process. The delamination issue is due to different surface polarities between metal and polypropylene-composite surfaces. One of the strategies to solve this issue is to modify the surface of one layer for creating similarity of the surface polarity. A metal sheet surface was coated with graphene using a cold spraying technique to enhance adhesion ability. The suitable spraying conditions were determined by experimenting with varying temperature, pressure, graphene quantity and graphene types. The effectiveness of surface modification by the graphene spraying technique was assessed by a surface morphology observation, an electrical conductivity measurement and DMFC performance tests. Results were interesting, they indicated that when DMFC was assembled with silver sheet, inserted BPs provided 25.13 mW/cm2 of power density, 3,350.7 mWh of generated energy and 67% of efficiency. This highlights that the performance of a BP prototype is superior to the performance of a commercial composite bipolar plate.