Iranian Journal of Materials Science and Engineering

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In this paper we have investigated the physical properties of reduced graphene oxide (RGO) thin films prepared at various substrate temperatures of 230, 260, 290, 320 and 350 ^oC using spray pyrolysis technique. We have compared these films from various viewpoints, including structural, morphological, optical, electrical and thermos-electrical properties. XRD analysis showed a phase shift from graphene oxide (GO) to RGO due to elevate the substrate temperature from 200 ^oC to higher temperatures. FESEM images of RGO thin films reveal that a stacked image of irregular and folding nanosheets, and rod-like features at temperatures below and above 290 ^oC; respectively. Optical studies showed that the layers have a relatively high absorption coefficient (∼0.8×10⁴ to 1.7×10⁴ cm⁻¹) in the visible range, with an optical band gap of 1.67–1.88 eV. The Hall effect data showed that all samples have a p-type conductivity with a hole concentration of ∼10¹⁵ cm⁻³, and sheet resistance values of about 10⁶ Ω/sq, in agreement with previous reports. The thermoelectric measurements revealed that with increasing applied temperature gradient between the two ends of the samples, the thermoelectric electromotive force (emf) of the prepared RGO thin films increases.

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Graphene oxide (GO) and reduced graphene oxide (rGO) is a semiconductor device which finds its many applications in the various electronic devices. In the present study GO and rGO thin sheets have been grown over Si wafers using Hummer’s and modified Hummer’s method and a comparison in the properties of the coatings have been carried out. The morphology of the sheets characterized by SEM revealed similar transparent sheet like structure for both the chemical synthesis. The diffraction pattern of GO and rGO prepared with modified Hummer’s method showed peak shift to lower diffraction angle from 9.96 ^o to 9.63 ^o and 26.4 ^o to 26.3 ^o respectively. The diffraction peaks were observed at diffraction phase of 001 and 002 crystal plane. FTIR spectra revealed presence of oxygen functional groups in GO thin sheets whereas peaks for oxygen functionalities are absent in rGO. The polarization curve indicated similar corrosion resistance of GO and rGO thin sheets grown under Hummer’s and modified Hummer’s. Capacitive property of rGO is better than GO as observed by the electrochemical analysis of GO and rGO..Graphene oxide (GO) and reduced graphene oxide (rGO) is a semiconductor device which finds its many applications in the various electronic devices. In the present study GO and rGO thin sheets have been grown over Si wafers using Hummer’s and modified Hummer’s method and a comparison in the properties of the coatings have been carried out. The morphology of the sheets characterized by SEM revealed similar transparent sheet like structure for both the chemical synthesis. The diffraction pattern of GO and rGO prepared with modified Hummer’s method showed peak shift to lower diffraction angle from 9.96 ^o to 9.63 ^o and 26.4 ^o to 26.3 ^o respectively. The diffraction peaks were observed at diffraction phase of 001 and 002 crystal plane. FTIR spectra revealed presence of oxygen functional groups in GO thin sheets whereas peaks for oxygen functionalities are absent in rGO. The polarization curve indicated similar corrosion resistance of GO and rGO thin sheets grown under Hummer’s and modified Hummer’s. Capacitive property of rGO is better than GO as observed by the electrochemical analysis of GO and rGO.

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The graphene oxide -TiO₂ (GO-TiO₂) and pre-reduced graphene oxide -TiO₂ (rGO-TiO₂) nanocomposites were fabricated successfully by hydrothermal method. The microstructure of synthesized nanocomposites was investigated using field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS) analysis. Moreover, galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) methods in three electrode system were applied to evaluate electrochemical properties. The results revealed that nanoparticles distributed more uniformly on graphene sheets, at lower concentrations of TiO₂. The rGO-TiO₂ and GO-TiO₂ nanocomposites showed 224 and 32 F/g specific capacitance at 5 mV s^-1 scan rate in 1 M KOH aqueous electrolyte, respectively. The pre-reduction of graphene oxide is the main reason for the better electrochemical performance of rGO-TiO₂ nanocomposite compared to GO-TiO₂ nanocomposite.

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In this work, the addition of a combination of Graphene Oxide Nanoplatelets (GONPs) and Ground
Granulated Blast Furnace Slag (GGBFS) was studied as admixture in concrete. Tests on physical and mechanical
properties and chloride permeability were conducted. GGBFS was replaced with Ordinary Portland Cement (OPC)
and it was determined that GGBFS Up to 50% by weight improves the physical and mechanical properties of
concrete. GONPs with an optimal amount of 50% by weight of GGBFS were added to the concrete and the physical
and mechanical properties of the samples were determined. It was observed that the addition of GONPs was effective
in improving the mechanical strength and physical properties of specimens. The results indicated that addition of
0.1 wt.% GO and 50 wt.% GGBFS would increase the compressive strength of the concrete sample up to 42.7%
during 28 days and 46% during 90 days compared to OPC. Concrete with a combination of 0.1 wt.% GONPs and
50 wt.% GGBFS witnessed an increase in its flexural strength up to 58.5% during 28 days and 59.2% during 90
days. The results indicated that by adding 0.1 wt.% GO and 50 wt.%, concrete chloride permeability decreased
substantially 72% for 90 day cured samples compared to OPC. GONPs as an alternative to cement up to 0.1% by
weight can accelerate the formation of C-S-H gel, thereby increasing the strength and improving the resistance of
water absorption and chloride permeability. The effects of pozolanic reaction in the concrete leading to the filling
of the pores were significant factors in the proposed curtailment mechanism