جستجوی مقالات مرتبط با کلیدواژه « اکسید گرافن » در نشریات گروه « مواد و متالورژی »

The purpose of this research is to investigate the effect of carbon black nanoparticles and graphene oxide on increasing the protective properties of epoxy coating on plain carbon steel. The results of the Kelvin scanning probe (SKP) test showed that in the sample containing carbon black nanoparticles and graphene oxide, exposure during three weeks In 100% humidity, the average surface voltage potential increased from -655 mV to -117 mV, while in the sample without the presence of nanoparticles, the surface voltage potential decreased from -329 mV to -506 mV in the same period of time. The presence of carbon black nanoparticles and graphene oxide in the coating prolongs the movement path of the electrolyte, including water, oxygen and corrosive ions, and delays the degradation of the epoxy coating.

The aim of this research is to improve the corrosion resistance and create the active inhibitory in hybrid-silane coatings. Therefor the graphene oxide (GO) nano-sheets and the methylene triphosphonic acid (ATMP) were used as a protective pigment and organic inhibitor carrier in the coating, respectively. The peaks appearing in 1059, 1380, 1730, and 3430 cm-1 belong to hydroxyl stretching, carbonyl, hydroxyl bending, and epoxide groups confirmed the successful synthesis of GO nanoparticles by infrared transfer spectroscopy (FTIR). The displacement of two peaks of 230 and 250 nm in GO to 261 and 360 nm in GO-ATMP represent the successful reduction of graphene oxide by ATMP molecules. Then, the corrosion resistance of GO-ATMP coating was evaluated using electrochemical impedance spectroscopy (EIS) and polarization tests. The results showed that the ATMP inhibitor improves the corrosion resistance properties of the coating, and the corrosion current density is reduced as 50%. After successfully inhibiting adsorption on GO plates, the coating (GO-ATMP) was applied on 2024 aluminum alloy sheets. The results of EIS and salt-spray tests showed that the corrosion resistance properties of GO-ATMP coatings improved due to restrict the access of corrosive environment to the metal surface. The intelligent releasing of the inhibitor during electrolyte penetration in scratched area of the coating was confirmed by the formation of a protective film in the scratch area in the electron microscope image of the sample. This caused to restrict the electrochemical reactions.

A smart nanostructured multilayered coating based on sol-gel/ polyelectrolytes/inhibitor/graphene oxide is developed via layer-by-layer (LbL) technique to provide effective corrosion protection for Al2024 substrates. The multilayered coating is consisting of a strong polycation (i.e., poly diallyldimethylammonium chloride (PDADMAC)), a weak polyanion (i.e., poly acrylic acid (PAA)), a corrosion inhibitor (i.e., Benzotriazole), and graphene oxide (GO). The local pH change in case of corrosion cause the loss of electrostatic attraction between polyelectrolytes, leading to increased permeability of the polyelectrolyte layer. Consequently, the corrosion inhibitor is released to prevent the corrosion process, providing a self-healing effect. Besides, the graphene oxide acts as a barrier layer, preventing the permeation of water and corrosive agents. The morphology, structure and chemical compositions are characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDS). To ensure the deposition of graphene oxide layer, Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy are performed. UV-visible spectrophotometry (UV-vis) is used to study the pH responsive release of corrosion inhibitor. To study the corrosion resistance and self-healing properties, electrochemical impedance spectroscopy (EIS) is performed in 3 % NaCl. The samples with polyelectrolyte layer show improved corrosion protection compared to the sol-gel sample (control). However, the samples with graphene oxide show the highest resistance, which is ~10X higher than the control sample after 2 weeks and its value is equal to 105.42 ohm.cm2.

Carbon is cheap and abundant in nature which can significantly reduce the cost of solar cell fabrication. In recent years, carbon nanostructures have gained special attention for application in perovskite solar cells. In this research, graphene oxide quantum dots (GOQDs) have been used in a planar perovskite solar cell. For this purpose, GOQDs with sizes smaller than 10 nm were synthesized by the hydrothermal method. The GOQDs were spin coated on ITO to make a planar n-i-p perovskite solar cell with the structure ITO/GOQD/MAPbI3/Spiro-OMETAD/Ag. The absorption spectrum of the GOQDs shows no overlap with absorption band of the MAPbI3 perovskite layer. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis show that a uniform film of crystalline MAPbI3 perovskite has been formed on the GOQD layer. The best device performance achieved in this research for the planar perovskite solar cell is as follows: Jsc=21.9 mA/cm2, Voc=1.02 V, FF=0.67 and PCE=15%.

The removal efficiency of methyl orange using two kinds of magnetic photocatalysts containing ZnO in the presence and absence of graphene oxide is investigated. Meanwhile, the kinetic of removal reaction of methyl orange, the effect of operational parameters such as irradiation time and weight fraction of photocatalysts based on statistical method and Duncan’s multiple range test are studied. The removal efficiency of methyl orange using both of the applied photocatalysts is affected by irradiation time and weight fraction of photocatalyst. So that the enhancement of these two parameters leads to the increment of removal efficiency of methyl orange. The results show that the kinetic reaction is pseudo first order. The rate of reaction using photocatalyst containing graphen oxide is higher than that of without it. The results of statistical analysis based on Duncan’s multiple range test reveals that both of the studied parameters have significant influence on the removal efficiency of methyl orange.

The Copper/Graphene oxide composite sheets, containing 2% graphene oxide were made by accumulative roll bonding method in four steps for the first time. The process was performed at ambient temperature and non-lubricating conditions. The initial materials were commercial pure copper and graphene oxide. In order to evaluation the produced composites the mechanical, microstructural, electrical and corrosion behavior of the produced composites were investigated at different ARB cycles. The mechanical properties of the composite were investigated by tensile, micro hardness and fractography tests before and at different stages of the process. To observe structural changes a field emission scanning electron microscopy (FESEM) equipped with an EDX spectrometer were used. The results have shown that no new phase has been produced in this composite, and only the main peak of the copper, graphene and oxygen elements could be observed in the EDX patterns.The observation of microstructure showed that in lower cycles, graphene oxide powders were more agglomerated and had non-uniform distribution and in the final stages the powders distribution was more uniformly. The fractography results revealed ductile fracture of the produced composites. The corrosion resistance and electrical conductivity of composites increased compared to pure copper

As to the crisis of energy in the recent years, devices manufacturing industry must be go toward the optimizing of energy consumption and increment in the lifetime leading to reduce production cost. Organic light emitting diodes (OLED) are one of the modern generations in the lighting industry that have many advantages such as being light and thin, flexibility, ability to be transparent, and easy to fabricate. These devices consist of hole injecting layer/electron and emissive layer. The main role of hole/electron injection layers is injection of charge carriers to emissive layer where electrons and holes recombinate and create photons. In this work we focused on optimization of hole injection in order to increase lifetime of device. We used the different composition of molybdenum oxide (MoOx) and graphene oxide (GO) in hole injection layer. The maximum efficiency of the devices owned to the composite thin film with 1:1 value ratio (MoOx:GO) that it could be reached to 7.5 lm/W.  The lifetime of the optimization of composite was compared to the standard device fabricated with PEDOT:PSS so that the results showed a 30 times enhancement in lifetime.

In this paper, the effect of graphene oxide (GO) nano-plates on the ballistic properties and energy absorption of Al6061 aluminum matrix composites produced by stir casting and hot rolling was investigated. The Al6061-Go nano-composites were fabricated by mixing GO nano-plates with weight percentages of 0.0, 0.2, 0.5 and 0.8, in the molten aluminum. Then, hot rolling was carried out at 530 °C on the cast samples. Mechanical behavior of nano-composites was investigated by performing quasi-static tensile tests. The perforation tests on the Al6061-GO plates, with the dimension of 60604.2 mm, was carried out using flat head projectiles with the aspect ratio of L/d >3, at the speeds of 100-300 m/s. The initial and residual velocity of projectiles was measured through 24 experiments, and the ballistic limit velocity was calculated for the fabricated nano-composites. The toughness, the fracture mode and energy absorption of the samples, were evaluated through the tensile and perforation tests, respectively. The results showed that by adding GO nano-plates, the ballistic limit velocity of the composite specimens improves by 24 % with respect to the base alloy. Also, the energy absorption of composite specimens in quasi-static and impact loading was respectively ameliorated by 116 % and 107 %. These results indicated that GO nano-plates are very effective on the energy absorption of 6061 aluminum alloy.

Nanoparticles are promising materials with a variety of applications, whose surface modification is an important technique for developing these applications. In this study, a new nanostructure was synthesized in four steps that can be used to remove pollutants from wastewater. Firstly, the graphene oxide nanoparticles (GO) were synthesized by the modified Hummer method, and then by simultaneous precipitation of ferrous and ferric ions in based atmosphere on the surface of GO, graphene oxide was magnetized. Subsequently, magnetic nanoparticles of graphene oxide (m-GO) coated by chitosan saccharide polymer with covalent bonding. The magnetic graphene oxide nanoparticles coated with chitosan (m-GO@Chi) were bonded to the cysteine-glutaraldehyde schiff’s base (CG) with cross-linking method and their surface modified with cysteine (m-GO@Chi-Cys). After that, the nanoparticle surface correction process was investigated by using og identification analyzes. The results of the FT-IR spectroscopy indicated that surface modification was successful at each stage and the presence of epoxide, carbonyl, amino, and thiol functional groups at the nanoparticles level was confirmed. According to FESEM images, GO particles were synthesized in two dimensional and average thicknesses of 29-165nm and after magnetization, iron oxide nanoparticles with a mean size of 35-50nm were observed at the GO level. VSM analysis was used to study the magnetic properties of nanoparticles. The absence of residues in the nanosize magneticization curve and the negligible reduction in the saturation magnetization of m-GO@Chi-Cys nanoparticles, as compared to m-GO, is due to the presence of thin layer of chitosan on the primary particles.

In this work, the amounts of the adsorption of conjugated polymers onto graphene/ graphene oxide were examined by reactive force-field molecular dynamics simulation. The polymers were poly(3-hexylthiophene) (P3HT) and poly(phenothiazine vinylene-polythiophene)(PTZV-PT). The length and width of the graphene sheet were 95.19 Å and 54.16 Å, respectively. The graphene oxide sheets with different oxidation percentages were considered. The molecular dynamics simulation results demonstrated a higher amount of adsorption onto graphene oxide sheets in comparison to graphene; furthermore, poly(phenothiazine vinylene-polythiophene) revealed a larger amount of adsorption in comparison with poly(3-hexylthiophene) in both functionalized groups of hydroxyl and epoxy. Also, some structural properties of polymers, such as radius of gyration of polymer and radial distribution function, were calculated at different reactive sites.

In this study, a nanocomposite of ZnV2O6 photo-catalyst hybridized with reduced graphene oxide (rGO) was prepared to degrade Rhodamine B. The ZnV2O6 nanostructures were successfully synthesized via co-precipitation route and the most significant process parameters were optimized during calcination. The structure and morphology were explored in detail using X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. Graphene oxide was synthesized from natural graphite powder using a modified Hummers method and reduced to graphene-like sheets by removing oxygen functionalities with the recovery of conjugated structure. The self-degradation of RhB is almost negligible, but when ZnV2O6 powders were inserted in the solution, the degradation of RhB increased to 44% after irradiation for 120 min. The ZnV2O6/rGO nanocomposites exhibit a much higher photocatalytic activity towards the photodegradation of dye, indicating that the presence of rGO can suppress charge recombination thanks to the fast interfacial electron transfer between ZnV2O6 particles and rGO sheets.

In this study, a multi nano biosensor was developed for simultaneous detection of carbon dioxide, methane, ethanol and ammonia gas, and its electrochemical response to various concentrations of these gases was studied. In the previous study, GO/PANI nanocomposite was constructed and examined the chemical composition and morphology and its structure by analyzing FT-IR, FE-SEM, HR-TEM and XRD. In this study, we put nanocomposite on silver-coated new electrodes and then, by placing nanoparticles of aluminum oxide, zinc oxide, tin oxide and titanium oxide, different parts of the sensor were compared to Carbon dioxide, Methane, Ethanol and Ammonia are susceptible, then, the response rate and its sensitivity to each of the gases were measured by amprometric tests. The results showed that the sensitivity of the multi nano biosensor is acceptable for sensing these gases. The results of the electrochemical experiments showed that the response of each sensor component is defined as an illuminated 4 equation to a mixture of the four gas discussed. Considering the responses of the four components of this multi nano biosensor simultaneously to the 4-gas mixture, 4 equations are obtained, which can be ascertained by the exact concentration of each of the four measured gases.Of course, these equations are correct until none of the sensors are saturated and there is no other effective gas in the analyte.

Well-known corrosion and wear resistance of electroless nickel phosphorus (NiP) coatings led studies on upgrading of mechanical and chemical properties and feasibility of its application in different industries. In this study, the effect of coating applying time on corrosion and wear resistance of the electroless nickel phosphorus-nano graphene oxide composite coating (NiP/GO) on st37 steel substrate was studied, comparing the simple electroless nickel phosphorus coatings. According to the polarization and electrochemical impedance spectroscopy results, NiP/GO deposit possessed more corrosion resistance than NiP coatings and the appropriate coating time was 60 minutes. The results also revealed that the presence of graphene oxide in nickel phosphorus coatings and increasing of coating applying time causes increasing of the coating microhardness by 279.8 HV and the friction coefficient by 19.33%.

Abstract Graphene based materials such as graphene oxide have been developed in the biomedical applications during recent years. In this research, graphene oxide/magnetite nanocomposite with drug controlled release ability was synthesized through coprecipitation on graphene oxide sheets. Phase analysis, particles morphology, magnetic properties, drug loading and release behavior of the synthesized nanocomposite was investigated using XRD, FESEM, VSM and UV-visible spectroscopy, respectively. XRD pattern showed formation of the graphene oxide/magnetite nanocomposite. FESEM images revealed that the mean particles size is 14 nm. The synthesized nanocomposite showed superparamagnetic characteristics while the saturation magnetization of the nanocomposite was 47 emu/g. Doxorubicin hydrochloride as an anti-cancer drug was loaded on the nanocomposite. Encapsulation efficiency and loading of the drug for the nanocomposite were 51.76% and 34.68%, respectively. The release model of the drug was best matched with Korsmeyer-Peppas model.

Graphene is a two dimentional crystal which made by a monolayer of carbon. It has a special electronic structure, which gives it unusual electronic, mechanical and thermal properties so that made it very useful for using in nanocamposits and even in an electronic industry. Although the graphene is a newfangled material, but these days graphene known as a vanguard of nanotechnology. The graphene oxide which consists of lots of functional groups could easily incorporate in many polymers and composites. Moreover, it is produced from rather cheap materials so it is an appropriate replacement for the most of organic and inorganic fillers. In this report the chemical structure of graphene and graphene oxide, synthesis methods which consist of micro-mechanical exfoliation, epitaxial growth, chemical vapor deposition, electrostatic deposition, upzipping of cabon nano tube and also chemical methods were depicted. So for improving its dispersing behavior in different matrix, different methods of functionalization of graphene were studied. The emphasis of this paper is on the functionalization of graphene surface even by covalancy or noncovalancy bond. Indeed this paper is a review of more than 110 different articles in this field.

In this research, based on graphene oxide nanocomposites were discussed. For this purpose, the well-known method of Hummers-Offerman of graphene oxide to graphene oxide by strong acid to convert and by using FT-IR, XRD and SEM, and its structure was confirmed as a good substrate for different reactions. After studies of the monomer in the Iranian market relatively easily accessible and were prepared, namely methyl methacrylate with different percentages were used for the preparation of polymer nanocomposites based on graphene oxide. Results improve heat resistance properties and the methyl methacrylate, the effect of increasing the weight percentage of graphene shows. Carboxyl functional groups in graphene oxide, which causes structural readily react with chemical monomers, can be also used as case study in the FT-IR was detected. This was also observed inSEMimage the addition of roughness of the polymer surface has been reduced graphene oxide can cause the mechanical properties of polymers can improved. Thus, the surface properties of the nanocomposites investigated and physical/mechanical properties such as electrical conductivity, thermal behavior, it is expected that the improved properties of nanocomposites and in subsequent reactions as suitable for other chemical reactions used or as well as a drug (drug carriers), or its application in the removal of toxic compounds in environmental water should be studied further.