Percentages Of Graphene Oxide Research Articles

Advanced Dentistry Biomaterials Containing Graphene Oxide.

The aim of this study was to obtain three experimental resin-based cements containing GO and HA-Ag for posterior restorations. The samples (S0, S1, and S2) shared the same polymer matrix (BisGMA, TEGDMA) and powder mixture (bioglass (La2O3 and Sr-Zr), quartz, GO, and HA-Ag), with different percentages of graphene oxide (0%, 0.1%, 0.2% GO) and silver-doped hydroxyapatite (10%, 9.9%, 9.8% HA-Ag). The physical-chemical properties (water absorption, degree of conversion), mechanical properties (DTS, CS, FS), structural properties (SEM, AFM), and antibacterial properties (Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans, Porphyromonas gingivalis, and Escherichia coli) were investigated. The results showed that the mechanical properties, except for the diametral tensile test, increased with the rise in the %GO. After 28 days, water absorption increased with the rise in the %GO. The surface structure of the samples did not show major changes after water absorption for 28 days. The antibacterial effects varied depending on the samples and bacterial strains tested. After increasing the %GO and decreasing the %HA-Ag, we observed a more pronounced antibacterial effect. The presence of GO, even in very small percentages, improved the properties of the tested experimental cements.

Influence of oxygen functional groups on the crack growth behavior of graphene with edge and middle crack: A molecular dynamics study

In the last decade, graphene has found a wide role and application in nanocomposites and nanodevices for its extraordinary properties. However, due to its low fracture toughness and brittleness, graphene is brittle, and crack growth occurs rapidly. As a result, crack growth behavior and control of its progression are important. In this study, molecular dynamics modeling was used to investigate the crack growth behavior and mechanical properties in functionalized graphene (with middle and edge crack) with different oxide groups (hydroxyl, epoxide, and carboxyl) at different percentages of graphene oxide (0–3 wt. %). The results show that functionalized graphene with oxide groups changes the properties of graphene, effectively reducing the crack growth in crack length (4.9 Å), crack opening displacement (1.4 Å), tensile strength for edge crack (74 to 54 Gpa), and middle crack (128 to 63 Gpa). Also, carboxyl and epoxide groups have a greater reduction in crack growth rate, opening displacement growth rate, and stress concentration. In addition, increase in the number of atoms in oxide groups around the initial crack (with radius 13 Å) reduces crack growth rate, opening displacement growth rate, and stress concentration. This study provides a broader insight into crack growth behavior in functionalized graphene with oxide groups.

Novel Graphene Oxide/Zinc Phthalocyanine Composites Bearing 3‐Chloro‐4‐Fluorophenoxy: Potential Usage for Sono/Photochemical Applications

AbstractThe aim of this paper is to explore the therapeutic contribution of graphene oxide (GO) to new sono/photosensitizers through sono/photochemical studies for the first time. For this purpose, new zinc (II) phthalocyanine bearing 3‐chloro‐4‐fluorophenoxy 2 was synthesized and then its GO‐based composites were prepared by non‐covalently coating ZnPc 2 on the graphene oxide surface. The photoactivity of these materials was compared and discussed in terms of their potential ability to be used in photosensitizer in photodynamic therapy (PDT) and sono‐photodynamic therapy (SPDT). In these application areas, GO can serve as photosensitizer carrier, while ZnPc 2 can be acting as PDT/SPDT agent. Therefore, phthalocyanine composites containing different percentages of graphene oxide by weight (wt.% GO) were prepared. SEM (scanning electron microscopy) results supported the interaction between GO and ZnPc 2. In the sono‐photochemical study, both ZnPc 2 and its composites gave very higher ΦΔ values than the photochemical study. The sono‐photochemical ΦΔ values were found to be 0.928 for 0 wt.% GO, 0.869 for 0.25 wt.% GO, 0.891 for 0.50 wt.% GO, 0.868 for 1 wt.% GO, 0.908 for 3 wt.% GO, 0.845 for 5 wt.% GO and 0.851 for 10 wt.% GO, respectively. According to obtained results, these materials could be promise as good photosensitizers for both the photochemical study and the sono‐photochemical study due to their very high singlet oxygen generation.

Influence of graphene oxide nano particle and aluminum powder on mechanical and thermal behavior of carbon fiber epoxy composite

Influence of graphene oxide nanoparticle and aluminium powder in carbon fiber epoxy composite was analysed in this experimental analysis. Three different compositions were developed based on the following combinations: Specimen 1 (Graphene oxide 3% − 15 gm and Aluminium 1.5% − 7.5 gm), Specimen 2 (Graphene oxide 6% − 30 gm and Aluminium 3% − 15 gm) and Specimen 3 (Graphene oxide 9% − 45 gm and Aluminium 4.5% − 22.5gm). The percentage of graphene oxide and aluminium are chosen depending upon the weight of resin (500 g) used for fabrication. The mechanical and thermal behavior of the developed composites were tested based on ASTM standards. Incorporation of 3 wt% of graphene oxide nano particle and 1.5 wt% of aluminium powder shows the best mechanical and thermal properties. Finite element analysis was performed to compare the static properties of aluminium alloy rim and the developed CFRP rim using ANSYS Workbench 18.2, infers that the CFRP rim had very high strength to weight ratio or specific stiffness than aluminium alloy rim.

Electrochemical noise analysis to evaluate the localized anti-corrosion properties of PP/graphene oxide nanocomposite coatings

• Electrochemical noise was used to evaluate the localized corrosion of PP-based NCCs. • PP|Graft|GO = 0.1 illustrated the best localized corrosion performance. • PP|Graft|GO = 0.1 was able to re-passive and prevent the growth of large & deep pits. • In the presence of GO, the transients shift to the higher frequencies at all times. Electrochemical noise analysis was applied to evaluate the localized anti-corrosion performance of polypropylene (PP)-based nanocomposite coatings (NCC). In this regard, the NCCs were developed on mild steel from a solution containing PP, MAH-grafted PP, and different percentages of graphene oxide (GO). The coated samples were subjected to thermal tests, salt spray, and electrochemical noise (EN) analysis. Electrochemical potential and current noise (EPN & ECN) signals were evaluated to find information about localized corrosion. First, the raw signals were analyzed based on the empirical mode decomposition (EMD), then the 3D diagrams (intensity, time, and frequency) were plotted using the Hilbert transform. The results showed in the presence of GO, the transients shift to the higher frequencies at all times, which confirms more tendency to uniform corrosion instead of localized. Introducing 3 wt% of GO NPs into the coating leads to the electrochemical noise resistance increasing by 5 times (>10 8 Ω.cm 2 ), pit initiation rate decreasing, and pit radius reduction (by ∼5 times). As a result, MAH-grafted PP and GO in these NCCs can act as effective barriers against corrosive agents, especially the agents that cause pitting corrosion.

Transport properties in spinel ferrite/graphene oxide nanocomposites for electromagnetic shielding

Herein, (Co0.5Ni0.5)Cr0.3Fe1.7O4/graphene oxide nanocomposites were fabricated by ultrasonication technique, using pure spinel ferrite and graphene oxide synthesized by sol-gel method and modified Hummers' method, respectively. The effect of graphene incorporation with ferrite nanoparticles was studied by X-ray diffraction (XRD), electrical and dielectric measurements. XRD analysis revealed the spinel phase for the ferrite sample and confirmed the formation of graphene oxide. The crystallite size was found in the range of 37−43 nm and the porosity increased with the increase in the concentration of graphene oxide in the composites. The DC electrical resistivity of spinel ferrite was found equal to 3.83×109 Ω.cm and it substantially decreased with the increase in the percentage of graphene oxide at room temperature. The real and imaginary part of relative permittivity followed the Maxwell-Wagner type of interfacial polarization. AC conductivity confirmed the conduction by hopping mechanism and increased on increasing the GO content. The coupling of magnetic ferrite with graphene oxide tunes the magneto-electrical properties for potential applications at high frequencies.

Physicochemical and electrochemical characterization of Ce/carbonaceous matrices-based composites

Ce/carbonaceous matrices-based composites with potential application in electrochemical processes were successfully produced. Ce-based MOF-76 (Metal Organic-Framework-76 family, formed by lanthanide ions coordinated to 1,3,5-benzenetricarboxylic acid ligand - H3BTC or simply BTC) was prepared with different percentages of graphene oxide (GO) in situ (named Ce-BTC-GOX%), then calcined to CeO2-rGOX%. All obtained materials were characterized by physicochemical techniques. The presence of carbonaceous matrices in the composites improves their thermal stability, alters particles shape, and decreases their size. All materials underwent Cyclic Voltammetry tests and selected composites were evaluated by Electrochemical Impedance Spectroscopy, Hydrogen Evolution Reaction and Oxygen Evolution Reaction. The electron transfer between Ce3+/Ce4+ redox pairs is observed around 1.3 and 1.2 V vs. Ag/AgCl(sat.KCl) for oxidation and reduction, respectively. Among all produced materials, the Ce-BTC-GO30% presented the best electrochemical response, reaching 0.506 A g−1 of anodic current and 19.92 C g−1 of charge density. Its capacitance reaches 3340.8 μF cm−2, while its resistance to charge transfer decreases (2.4 Ω cm2) and Tafel equation slopes are 84.3 mV dec−1 for HER and 60.5/127.9 mV dec−1 for OER.

Workability, microstructure, strength properties and durability properties of graphene oxide reinforced cement paste

ABSTRACTGraphene oxide (GO) is one of the prominent nanomaterial, this has been utilised in the cement composite materials. Graphene oxide represents unprecedented range of properties with a potential to enhance the strength and toughness of cement-based composites. In this study, the influence of graphene oxide was evaluated on the workability, microstructure, strength and durability properties of the fresh and hardened cement composites. Different percentages of graphene oxide were added at 0wt%, 0.01wt%, 0.02wt%, 0.03wt% and 0.04wt% by weight of cement. Workability in terms of fluidity, setting time and viscosity tests were conducted to the fresh GO-cement paste samples. Compressive and flexural strength tests were conducted to the hardened GO-cement paste samples at 28 days. Through scanning electron microscopy (SEM), morphology and microstructure of hardened cement paste were investigated and XRD technique was assisted in identifying the crystalline materials and studying the phase composition of cement composites. Results exhibited that, graphene oxide addition increases the viscosity, decreases the fluidity and shortens the setting time of the cement paste. Increased compressive and flexural strength results were appeared due to the addition of graphene oxide at different dosages. At 0.04wt% of graphene oxide dosage, the compressive strength was increased by 46.6% and flexural strength was increased by 75% than normal cement paste at 28 days. Water permeability of the cement composite specimens was highly reduced due to the graphene oxide reinforced infiltration barrier, which leads to the improvement in durability.

Synthesis and characterization of hybrid composite aerogels from alginic acid and graphene oxide

Aerogels are one class of solid adsorbents that are gaining considerable attention because of their very high porosity, high specific surface area, and extremely low density. However, most aerogels being studied and used recently are synthetic in nature, which are usually mesoporous silica and metal-organic frameworks (MOFs). As research focus is geared towards sustainable engineering, it is desired to utilize biomass to synthesize aerogels. This study thus aims to produce alginic acid-graphene oxide hybrid composite aerogels and compare them with its existing synthetic counterparts. Alginic acid (AA) is an abundant marine biopolymer that easily forms gels, while graphene oxide (GO) is a nanomaterial consisting of many functional groups. Aerogels made up of AA and GO were successfully synthesized using a sol-gel method. The hydrogel was converted into an aerogel by drying with supercritical carbon dioxide. The percentage of graphene oxide was varied from 0 to 20%. The aerogels were characterized by scanning electron microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and nitrogen adsorption–desorption measurements. The addition of GO increased the specific surface area of the aerogel up to a certain point, after which it decreased. The 10% GO-AA aerogel showed the most favourable porosity characteristics with a specific surface area of 177.26 m2/g and average pore diameter of 53.2 nm. There had been no observable difference in the thermal behaviour of the aerogels with a change in the concentration of graphene oxide.

Nanosized Cu-MOFs induced by graphene oxide and enhanced gas storage capacity

Various MOFs with tailored nanoporosities have recently been developed as potential storage media for CO2 and H2. The composites based on Cu-BTC and graphene layers were prepared with different percentages of graphene oxide (GO). Through the characterization analyses and gas adsorption experiments, we found that the nanosized and well-dispersed Cu-BTC induced by the incorporation of GO greatly improved the carbon dioxide capture and hydrogen storage performance of the composites. The materials obtained exhibited about a 30% increase in CO2 and H2 storage capacity (from 6.39 mmol g−1 of Cu-BTC to 8.26 mmol g−1 of CG-9 at 273 K and 1 atm for CO2; from 2.81 wt% of Cu-BTC to 3.58 wt% of CG-9 at 77 K and 42 atm for H2). Finally, the CO2/CH4 and CO2/N2 selectivities were calculated according to single-component gas sorption experiment data.