Bulk g-C3N4 has very poor photocatalytic activity. Many methods have been utilized to increase the photocatalytic performance of this semiconductor. Here, a simple preparation was used to create exfoliated g-C3N4 that was co-doped with sodium and tungsten. The produced Na-W co-doped exfoliated g-C3N4 was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis spectroscopy, and Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS). The doping samples with Na and W changed the band structure of the g-C3N4 lattice, which increased light absorption and caused a reduction in the band gap. The samples had layered morphology. After exfoliation and sodium and tungsten co-doping of the samples, the methylene blue photodegradation was greatly enhanced. The doping of the samples also had an impact on the dye adsorption capacity. The dye removal activity of the Na-W co-doped exfoliated g-C3N4 sample is higher than those of pure bulk g-C3N4 and pure exfoliated g-C3N4. The rate reaction constant (k) of the Na-W co-doped exfoliated g-C3N4 is up to 3.3 times greater than that of bulk g-C3N4. The produced photocatalyst may be utilized for the treatment of wastewater comprising methylene blue as the pollutant agent.

High-temperature erosion-oxidation (E-O) of Ni-20Cr-(0-30)Fe-(0-4)Si was investigated in fluidized bed waste incineration conditions. The specimens were tested in a rig for 250 h, under the collision of hot silica sand contaminated with 0.5 wt.% of NaCl-KCl salt mixture at a temperature of 700 °C. To have a better understanding of the materials’ behavior, the specimens were also oxidized at 560 °C for 100 h in the atmosphere of air + chlorine vapors. The thickness reduction and mass gain of the specimens were used to evaluate the materials under E-O and oxidation conditions, respectively. The specimens were studied using FESEM, EDS, and XRD analysis. At E-O conditions, Ni-20Cr showed the highest material loss (~17.6 mm). The addition of 30 wt.% of Fe to the alloy decreased the wastage to about 6.7 mm. The E-O resistance of Ni-20Cr-30Fe-4Si was about two times lower than the Si-free alloy which indicates that Si had a detrimental effect on the E-O resistance of the alloys. Under oxidation conditions, Ni-20Cr-30Fe showed the highest resistance with a mass gain of about 0.1 mg/cm2. The addition of 4 wt.% Si caused a dramatic decrease in the oxidation resistance of the alloy (mass gain of ~3.8 mg/cm2). The addition of Fe stimulated Cr2O3 scale formation by which the higher E-O and oxidation resistance of the alloy were confirmed. In Ni-20Cr, the formation of a multi-component scale, and in Ni-20Cr-30Fe-4Si, a porous surface scale formed through active oxidation were possibly responsible for the poor performance of these alloys.

In this paper, we aimed to investigate the linear and nonlinear optical properties of reduced graphene oxide-based metal oxide nanocomposite in comparison with reduced graphene oxide (RGO) and the effect of the process of reducing the oxygen groups of graphene oxide on the change of the nonlinear absorption coefficient of the reduced graphene oxide- zinc oxide (RGO-ZnO) and reduced graphene oxide-zinc oxide-iron oxide (RGO-ZnO-Fe2O4) sample. For this purpose, RGO, RGO-ZnO, and RGO–ZnO-Fe2O4 were synthesized using Hummers and hydrothermal methods, respectively, and then were analyzed using Fourier transform infrared (FT-IR), Ultraviolet-visible absorption (UV-Vis), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) were characterized. The XRD and FTIR analysis successfully synthesized RGO-ZnO and RGO-ZnO-Fe2O4 nanocomposites. Also, FT-IR spectroscopy indicated that absorption bands at 3340 cm-1, 1630 cm-1, 1730 cm-1, and 480 cm-1 are related to O-H, C=C, C=O, and Zn-O stretching vibrations, subsequently. The direct energy gap of GO, RGO, RGO-ZnO, and RGO-ZnO-Fe2O4 from UV-Vis spectra was reported to be 3.36, 3.18, 3.25, and 2.7eV, respectively. In addition, the third-order nonlinear optical properties (the nonlinear absorption coefficient) of all samples were investigated using the Z-scan technique with Nd: YAG laser (532 nm, 70 mW), and it was observed that the third-order nonlinear optical properties were increased from 8.3×10-4cm/W for RGO to 5.6×10-3 cm/W for RGO-ZnO-Fe2O4.

In Gas Metal Arc Welding (GMAW), the applied thermal cycle will cause a change in the chemical composition and structure of the welded zone compared to the base metal (BM). As a result, it causes changes in mechanical properties including fatigue strength. This research investigates the tensile test, hardness, and fatigue properties of A36 low-alloy marine steel with high tensile strength. For this purpose, A36 low-alloy marine steel was welded by the GMAW method. After performing the mechanical tests, the structural examination was done by optical microscope (OM) and Atomic Force Microscope (AFM) on the welded samples. The obtained results show that the fatigue strength of the weld has decreased compared to the base metal by creating coarse and heterogeneous grain structures, which are caused by the effects of the mentioned items in the weld metal. Microstructural defects in the weld metal caused cracks germination and accelerated crack growth. So that the fatigue strength of the weld metal was lower than that of the BM.