Mariam Al Ali Al-Maadeed

Melt processing and characterisation of polyamide 6/graphene nanoplatelet composites

Graphene, due to its outstanding properties, has become the topic of much research activity in recent years. Much of that work has been on a laboratory scale however, if we are to introduce graphene into real product applications it is necessary to examine how the material behaves under industrial processing conditions. In this paper the melt processing of polyamide 6/graphene nanoplatelet composites via twin screw extrusion is investigated and structure–property relationships are examined for mechanical and electrical properties. Graphene nanoplatelets (GNPs) with two aspect ratios (700 and 1000) were used in order to examine the influence of particle dimensions on composite properties. It was found that the introduction of GNPs had a nucleating effect on polyamide 6 (PA6) crystallization and substantially increased crystallinity by up to 120% for a 20% loading in PA6. A small increase in crystallinity was observed when extruder screw speed increased from 50 rpm to 200 rpm which could be attributed to better dispersion and more nucleation sites for crystallization. A maximum enhancement of 412% in Youngs modulus was achieved at 20 wt% loading of GNPs. This is the highest reported enhancement in modulus achieved to date for a melt mixed thermoplastic/GNPs composite. A further result of importance here is that the modulus continued to increase as the loading of GNPs increased even at 20 wt% loading and results are in excellent agreement with theoretical predictions for modulus enhancement. Electrical percolation was achieved between 10–15 wt% loading for both aspect ratios of GNPs with an increase in conductivity of approximately 6 orders of magnitude compared to the unfilled PA6.

Oleic acid-grafted chitosan/graphene oxide composite coating for corrosion protection of carbon steel

An anticorrosion coating film based on the formation of nanocomposite coating is reported in this study. The composite consisted of chitosan (green matrix), oleic acid, and graphene oxide (nano filler). The nanocomposite coating was arranged on the surface of carbon steel, and the corrosion resistance was monitored using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP). Compared to the pure chitosan (CS) coating, the corrosion resistance of oleic acid-modified chitosan/graphene oxide film (CS/GO-OA) is increased by 100 folds. Since the well-dispersed smart grafted nanolayers delayed the penetration rate of corrosive species and thus maintained long term anticorrosive stability which is correlated with hydrophobicity and permeability.

Stretchable Electrospun PVDF-HFP/Co-ZnO Nanofibers as Piezoelectric Nanogenerators

Herein, we investigate the morphology, structure and piezoelectric performances of neat polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) and PVDF-HFP/Co-ZnO nanofibers, fabricated by electrospinning. An increase in the amount of crystalline β-phase of PVDF-HFP has been observed with the increase in Co-doped ZnO nanofiller concentration in the PVDF-HFP matrix. The dielectric constants of the neat PVDF-HFP and PVDF-HFP/2 wt.% Co-ZnO nanofibers are derived as 8 and 38 respectively. The flexible nanogenerator manipulated from the polymer nanocomposite (PVDF-HFP/Co-ZnO) exhibits an output voltage as high as 2.8u2009V compared with the neat PVDF-HFP sample (~120u2009mV). These results indicate that the investigated nanocomposite is appropriate for fabricating various flexible and wearable self-powered electrical devices and systems.

High performance sulfonic acid doped polyaniline–polystyrene blend ammonia gas sensors

In this work, we present a method of preparation and sensing measurement of four camphorsulfonic acid (CSA) doped polyaniline–polystyrene blends (PANI–PS), where PANI is obtained by dispersion polymerization and blending is conducted by casting method. The effect of CSA concentrations on morphological, optical, thermal and electrical properties has been thoroughly analysed. Interestingly, the morphological analysis (SEM) exhibits different sizes of nanoparticle structures, whereas the FTIR spectra show chemical interaction between the two polymers. DSC data clearly reflects that the blend films carry combined physical properties of both the polymer components. The electrical properties are studied by in-plane I–V characteristics and four probe conductivity measurements. Finally, the blends with high conductivity seem to have good sensitivity and reversibility when used as NH3 sensors.

Improved flexible, controlled dielectric constant material from recycled LDPE polymer composites

In this study, recycled low density polyethylene (RLDPE) is developed with the addition of aluminum oxide (Al2O3) to have new polymer composites. The following wt% were used of the filler (1, 4 and 6xa0wt%). Tensile properties, Hardness, scanning electron microscopy (SEM) thermo gravimetric analysis, differential scanning calorimetry and dielectric properties were studied for these composites. 4xa0wt% Al2O3/RLDPE composites showed the optimum values of 15.52, 180.8 and 59.72xa0MPa for the tensile strength, tensile modulus and hardness were reported. Increasing the filler % decreased the mechanical properties of the composites due to agglomeration and poor surface contact with the polymer matrix. This is confirmed by SEM studies. Al2O3 filler increased the melting and crystallization temperature of RLDPE. Furthermore, it showed that Al2O3 filler improved the thermal stability of RLDPE with increasing the % of filler. Relative permittivity, dielectric loss factor and AC electrical conductivity were increased with increasing the amount of the AL2O3. The relative permittivity reached a value of 4.9 at 1xa0kHz frequency, which is a good value for a flexible composite prepared from recycled material and it can be used in electrical devices and electronic packaging.

Flexible tri-layer piezoelectric nanogenerator based on PVDF-HFP/Ni-doped ZnO nanocomposites

In this work, we report Ni doped ZnO/poly(vinylidene fluoride-hexafluoropropylene) [PVDF-HFP] nanocomposites prepared by sandwiching and their structural, morphological, thermal, electrical and piezoelectric properties. The X-ray diffraction analysis and Fourier transform infrared spectral (FTIR) studies of the nanocomposite films confirm the enhanced β-phase crystallization in the PVDF-HFP matrix due to the Ni-doped ZnO nanoparticles. Microscopic images of the prepared samples substantiate homogeneous dispersion of Ni-doped ZnO nanoparticles in the polymer matrix resulting in higher β-phase nucleation. In addition, the nanocomposite shows a high dielectric constant and low dielectric loss, making it suitable for energy storage. The piezoelectric property increases with the filler concentration and a maximum generated output voltage of 1.2 V is achieved at 0.5 wt% Ni-doped ZnO.

Nanoflower-like Yttrium-doped ZnO Photocatalyst for the Degradation of Methylene Blue Dye

Pure ZnO and Yttrium‐doped (Y‐doped) ZnO at various mol% with flower‐like nanostructures are synthesized by a microwave‐assisted sol–gel method, followed by investigating the morphologies, crystal structures, optical properties and photocatalytic performances. While the phase formations are detected by X‐ray diffraction technique, both scanning and transmission electron microscopy images clearly depict the flower‐like morphology of ZnO and Y‐doped ZnO samples. Formation of flower petals is from the nanoparticles that grew and connected by orientation attachment process. The flower‐like architecture is addressed in terms of an Ostwald ripening mechanism. The UV‐Vis absorption studies show enhanced absorption for the Y‐doped ZnO, whereas the photoluminescence spectra confirm the significance of sample defects in the photocatalytic degradation of organic pollutants. Effects of various experimental parameters such as the amount of photocatalysts, dye concentration and dopant concentration on the dye degradation are also optimized.

In-vitro biocompatibility, bioactivity and photoluminescence properties of Eu3+/Sr2+ dual-doped nano-hydroxyapatite for biomedical applications

In the present investigation, we have successfully synthesized luminescent Eu3+ -doped and Eu3+ /Sr2+ codoped hydroxyapatite (HA) nanoparticles through sol-gel assisted precipitation method with the aim of developing novel biomaterials containing osteoblast mineral (Sr2+ ) and luminescence activator (Eu3+ ). The structure, morphology, thermal stability, and luminescence properties of the resultant spherical nanoparticles (50-100 nm diameters) were studied. Moreover, the in-vitro bioactivity of Eu0.1 Sr0.1 HA nanoparticles was investigated by immersing in the simulated body fluid for many weeks. The antimicrobial activity results against gram positive and gram negative bacterial stains, showed better resistivity for the Eu0.1 Sr0.1 HA among the other compositions. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay of live/dead cells cultured with Eu3+ /Sr2+ -doped HA nanoparticles retained its normal morphology and did not show a significant impact on cell proliferation at various incubation days, which evidence for the materials superior biocompatible nature even at a higher concentration of 375 µg/mL. Thus, the incorporation of dual ions in HA nanoparticles with strong luminescence properties develops potential biomaterial for live cell imaging and in nanomedicine.

Optimization and Prediction of Mechanical and Thermal Properties of Graphene/LLDPE Nanocomposites by Using Artificial Neural Networks

The focus of this work is to develop the knowledge of prediction of the physical and chemical properties of processed linear low density polyethylene (LLDPE)/graphene nanoplatelets composites. Composites made from LLDPE reinforced with 1, 2, 4, 6, 8, and 10u2009wt% grade C graphene nanoplatelets (C-GNP) were processed in a twin screw extruder with three different screw speeds and feeder speeds (50, 100, and 150u2009rpm). These applied conditions are used to optimize the following properties: thermal conductivity, crystallization temperature, degradation temperature, and tensile strength while prediction of these properties was done through artificial neural network (ANN). The three first properties increased with increase in both screw speed and C-GNP content. The tensile strength reached a maximum value at 4 wt% C-GNP and a speed of 150u2009rpm as this represented the optimum condition for the stress transfer through the amorphous chains of the matrix to the C-GNP. ANN can be confidently used as a tool to predict the above material properties before investing in development programs and actual manufacturing, thus significantly saving money, time, and effort.

Vapor sensing performances of PVDF nanocomposites containing titanium dioxide nanotubes decorated multi-walled carbon nanotubes

Inorganic nanocarbon hybrid materials are good alternatives for superior electrochemical performance and specific capacitance to their traditional counterparts. Nanocarbons act as a good template for the growth of metal nanoparticles on it and their hybrid combinations enhance the charge transport and rate capability of electrochemical materials without sacrificing the specific capacity. In this study, titanium dioxide nanotubes (TNT) are synthesized hydrothermally in the presence of multi-walled carbon nanotubes (MWCNT) where the latter acts as base template material for the metal oxide nanotube growth. The MWCNT–TNT hybrid material possesses very high dielectric strength and this is used to enhance the dielectric property of the polymer polyvinyledene fluoride (PVDF). Solution mixing was used to prepare the PVDF/MWCNT–TNT nanocomposites by varying the filler concentrations from 0.5 to 2.5xa0wt%. Excellent vapor sensing was noticed for the PVDF nanocomposites with different rate of response towards commonly used laboratory solvents. The composites and the fillers were characterized for its morphology and structural properties using scanning and transmission electron microscopy, X-ray diffraction studies and infrared spectroscopy. Vapor sensing was measured as relative resistance variations against the solvent vapors, and the dielectric properties of the composites were measured at room temperature during the frequency 102–107xa0Hz. Experimental results revealed the influence of filler synergy on the properties of PVDF and the enhancement in the solvent vapor detectability and dielectric properties reflects the ability of these composite films in flexible vapor sensors and in energy storage.