Search

The energy required for joining steel segments by using laser welding is relatively very low compared with arc welding, gas welding, or any other conventional welding techniques. Moreover, the rapid cooling may create a significant effect on different regions, such as the fusion zone (FZ), heat affected zone (HAZ), and base metal (BM), and in turn affect different parameters. In this study, the characteristics of the laser-welded joint were investigated by varying laser power, welding velocity and incident angle, and tensile strength. In our, experiments. the microhardness was increased by varying the power of laser welding. The strength of the joint was increased to 549 MPa with 2200 W high power, 30 mm/s velocity, and 80º laser incident angle. By increasing the power and velocity of the laser, the welding gun strength was improved; conversely, the angle of laser incident on the welding location decreased while its strength was increased.

Graphitic carbon nitride (g-C3N4) is paying attention lately owing to its interesting characteristics and substantial application in improving environmental and energy concerns. Nevertheless, the photocatalytic activity of g-C3N4 is constrained by the inertness of the surface and particle aggregation during photocatalytic activity. Herein, we report the preparation of g-C3N4 with honeycomb-like morphology (HC-C3N4) via thermal condensation of prepared SiO2 templates and dicyandiamide. The etching out of the SiO2 templates by NH4HF2 created hollow or macropores in the C3N4 matrix resulting in its structural changes. Similar, to the bulk C3N4, the HC-C3N4 exhibited higher photocatalytic CO2 reduction in hydrocarbons. This improved photocatalytic achievement is associated with higher specific surface area, excellent visible light absorption capability, higher electron donor density, easy mass diffusion of materials for surface reaction, and effective segregation of photogenerated charge carriers. Furthermore, the HC-C3N4 honeycomb structure was deposited with Ni(OH)2 clusters which showed remarkable CO2 reduction activity of 1.48 μmolh−1 g−1 of CH4 and 0.73 μmolh−1 g−1 of CH3OH generation which is 3.5 and 4.3 times higher CO2 reduction activity compared with bulk C3N4 clustered with Ni(OH)2 particles. This comprehensive study demonstrated that HC-C3N4 nanostructured polymeric semiconductor is envisaged to have great potential in the application of a variety of fields such as photocatalysis, sensor technology, and nanotechnology.

In this study, ZnO/ZnS hierarchical nanobranch like composite with Cu(OH)2 clusters were designed via a simple facile hydrothermal process followed by precipitation reaction. Anchoring Cu(OH)2 clusters on the ZnO/ZnS composite surface can shorten the charge migration distance, providing abundant active sites and extend the visible-light absorption. The effects of Cu(OH)2 clusters loading on the photocatalytic application were investigated. The photocatalytic activities for hydrogen production were evaluated under visible-light (λ > 400 nm) irradiation. It was found that coupling suitable weight ratio of Cu(OH)2 cluster over the ZnO/ZnS nanobranches will enhance the photocatalytic hydrogen evolution by 46.5 and 13.7 times higher than pure Zn5(CO3)2(OH)6 and ZnO/ZnS, nanobranches respectively and an apparent quantum efficiency of 11.5% at λ = 420 nm, and 14.7% under monochromatic LED light irradiation of 520 nm wavelength was achieved. This results show that construction of ZnO/ZnS nanobranches decorated with Cu(OH)2 clusters can effectively improve the charge transfer and enhance the photocatalytic hydrogen production. The as-prepared ZnO/ZnS nanobranches decorated with Cu(OH)2 clusters exhibits outstanding stability and recyclability. The mechanism for the enhanced hydrogen evolution is also discussed.

Graphitic carbon nitride (g-C

The orthorhombic perovskite, Gadolinium aluminum oxide (GdAlO3, GAP) material was successfully prepared by hydrothermal supercritical fluid method using co-precipitated gel of GAP. All experiments were carried out in the pressure and temperature ranges of 100–150 MPa and 180–650 °C respectively. The as-prepared GAP samples were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray spectroscopy (EDS), thermo gravimetry (TGA) and differential thermo gravimetry analysis (DTA). The XRD profile confirms fully crystalline and orthorhombic nature of as-prepared materials, which is well correlated to the reported results. The SEM studies reveal that the GAP materials synthesized at 650 °C/150 MPa for 92 hrs possesses polycrystalline nature with average particle size in the range of 5–20 µm. The DTA shows a crystallization peak at 361 °C at this temperature the agglomerated GAP gel starts to crystallize into polycrystalline GAP materials. When compared with other methods, like sol-gel and solid-state reactions our crystallization temperature is very much lower and feasible. This work not only demonstrates a simple way to fabricate GAP polycrystalline materials from co-precipitated gels but also shows a possible utilization of same technique for synthesis of other high temperature materials.

Converting CO2 into renewable solar fuel using photocatalysts is one of the most ideal solutions for environmental challenges and energy crises. Here, the solid-solid Z-scheme Zn0.5Cd0.5S/Au@g-C3N4 (ZCS/Au@CN) heterojunction showed improved photocatalytic reduction of CO2 due to the enhanced visible light consumption, fast dissolution of photogenerated electron-hole pairs, quick interfacial transfer process of electrons, and enlarged surface area. Under visible-light irradiation, methanol (CH3OH) was produced at a rate of 1.31 μmol h−1 g−1 over ZCS/Au@CN, roughly 43.6 and 32.7 folds higher than those observed over pure ZCS and CN samples. The analytical characterization results verified the role of AuNPs as an electron mediator, which improved the rapid extraction of photoinduced electrons and enhanced the reduction ability of CO2. This work not only demonstrates a facile photodeposition assisted hydrothermal method for fabrication of ZnxCd1-xS/Au@C3N4 heterojunction composite photocatalysts but also demonstrates the possibility of utilizing ternary composites for enhanced photocatalytic reduction of CO2.

Transition metal chalcogenides with abundant active edge sites and suitable structures for large-scale water splitting in alkaline hydrogen evolution reaction (HER) are challenging but promising. Herein, hierarchical heterostructured nickel foam–supported Co3S4 nanorod arrays embellished with edge-exposed MoS2 nanoflakes (Edge-MoS2/Co3S4@NFs) as an effective HER catalyst are designed. There into, porous nickel foam and moderately distributed nanorod arrays of Edge-MoS2/Co3S4@NFs provide multiscale pathways for efficient charge and mass transport and significantly enlarge the surfaces for the deposition of MoS2 flakes. The superhydrophilic/aerophobic surface improves the electrolyte transport and facilitates the detachment of hydrogen bubbles from the surface of the catalyst. The MoS2 flakes anchored on nanorods are well dispersed with plentiful active sites exposed which enhance the intrinsic activity of active sites owing to the adequate intersection of charge and mass. In addition, there is a synergetic effect of bimetal sulfides, evidenced by increasing the turnover frequency. Therefore, the Edge-MoS2/Co3S4@NF affords a low overpotential (η10 = 90.3 mV and η1000 = 502.0 mV) and small Tafel slope (61.69 mV dec−1). This study provides a facile strategy to develop electrocatalysts through the synergy of enhanced thermodynamic and kinetic processes, shedding lights on the advanced design of functional materials for energy chemistry.

The optical and catalytic performances of materials strongly depend on their size, morphology, dimensionality and structure. Herein, we demonstrate a facile one-pot template free synthesis of hierarchical CdMoO 4 porous microspheres via a simple low temperature oil bath method. The photoactivity of the as-prepared samples was evaluated by photocatalytic decolorization of Methyl Orange (MO) and Methylene Blue (MB) mixed dye aqueous solutions at ambient temperature under full solar spectrum. The results indicated that the concentration of ammonium molybdate and reaction time greatly influence the diameter, average crystallite size, specific surface area, pore structure and photocatalytic activity of the prepared samples. Especially, under the suitable conditions the prepared hierarchical CdMoO porous microspheres exhibited enhanced photocatalytic activity and high stability. Furthermore, it is found that the photocatalytic activity and formation rate of hydroxyl radicals greatly depend on the particle sizes and morphology of as-prepared samples. This work not only demonstrates a simple way to fabricate the hierarchical CdMoO 4 porous microspheres but also shows a possibility for utilization of CdMoO 4 porous microspheres for the photocatalytic treatment of waste water pollutants.

Carbon dioxide (CO2) extent in the atmosphere has gradually increased because of excessive activities such as burning fossil fuels and deforestation. Converting CO2 into value-added hydrocarbon fuels over semiconductors by using solar energy is thus essential to reduce the greenhouse effect. In this study, novel hierarchical graphene–Zn0.5Cd0.5S (xG-ZCS) nanocomposites were constructed through a straight forward dual-step hydrothermal approach at 180 °C. The prepared composites exhibited enhanced visible-light photocatalytic transformation of CO2 to methanol (CH3OH). The 2G-ZCS (2 wt% graphene-Zn0.5Cd0.5S) composite produced the highest amount of CH3OH (approximately 1.96 μmol g−1 h−1), that is almost 98 times greater than pure ZCS nanospheres (Zn0.5Cd0.5S). The increased photocatalytic CO2 reduction could be as a result of graphene, which served as an exceptional electron receiver and carrier, sinking the reconsolidation of charge mobility and enhance the catalytic property. The electrochemical impedance spectroscopy and transient photocurrent analysis was analyzed to demonstrate the proposed photocatalysis mechanism.

In this study, the characterization of laser weld joint on transformation-induced plasticity (TRIP) steel sheets coupled with Nd:YAG laser welding was investigated, and the influence of welding conditions like angle of weld, power of laser, and welding speed on the strength of the joint was measured. The microstructure, tensile behavior, and microhardness of TRIP laser-welded sheets were examined in detail. The power was maintained constant, i.e., 1800 W, and by relatively varying the velocity from 25 to 30 mm/s, the strength of the joint increased drastically to 11%. In contrast, by varying the power, the effect of velocity was reduced; however, the point performance was enormously stable. Finally, the microhardness behavior of the heat-affected zone and fusion zone was investigated and discussed.

CdMoO4@CdS core-shell hollow microspheres with the diameter of 2-3 μm were synthesized through a simple ion exchange hydrothermal method by using CdMoO4 solid microspheres as the sacrificial template in the presence of thioacetamide (TAA). Based on the detailed investigation it was found that the concentration of TAA in the starting solution affects the size of the CdS nanosheets and the hollowing process. At the TAA concentration of 0.1 M, CdMoO4@CdS core-shell hollow spheres with a CdS nanosheet thickness of 50-100 nm were obtained. The formed CdS nanosheets have a hexagonal wurtzite structure and exhibit good size uniformity and regularity. Furthermore, the photocatalytic activity of the as-prepared samples was evaluated towards degradation of Rhodomine B (RhB) aqueous dye solution under visible-light. Compared to CdMoO4 microspheres, CdMoO4@CdS core-shell hollow microspheres show enhanced photocatalytic activity. The observed photocatalytic performance was attributed to the synergetic effects of composite morphology, pore structure, and exposed two-dimensional (2D) CdS nanosheets with dominant 001 facets in CdMoO4@CdS core-shell hollow microspheres. Furthermore, the growth mechanism of CdMoO4@CdS hollow microspheres was discussed in detail.

The positron annihilation lifetime spectroscopy (PALS) of cavansite crystals collected from Wagholi, Pune district of Western Maharastra, India were characterized by 60Co gamma radiation with an irradiation dose of 1 Mrad and 3 Mrad at ambient conditions. The influence of γ-irradiation on the pore size and its content on cavansite structure were examined. The studies suggest ortho-positronium (o-Ps) lifetime (τ 3) and intensity (I 3) decreased upon γ-irradiation. The decreased o-Ps lifetime (τ 3) is attributed to the collapse of the framework structure of cavansite crystal. In addition, the reduction in o-Ps intensity (I 3) is known to decrease o-Ps annihilation sites because of free radical reactions.

Certain silicate materials with different crystal structures show excellent luminescence properties. Furthermore, these silicate compounds have high chemical and thermal stability and considered as an excellent phosphor host materials. In this study, we report (Gd1−xEux)3BSi2O10 as a novel ultraviolet (UV) excited white phosphors prepared under solid state reaction and their luminescence properties at 393 nm excitation were investigated in detail. The as prepared (Gd1−xEux)3BSi2O10 phosphors showed red emission with UV (around 580–630 nm) and near-UV light (around 250–410 nm). The chromaticity coordinates (0.60, 0.34) of the prepared borosilicate phosphor were very close to the NTSC standard value (0.67, 0.33) and its emission intensity was almost similar to commercial red phosphor Y2O2S:0.05Eu3+. Further, as prepared (Gd1−xEux)3BSi2O10 material is considered to be an efficient red-emitting phosphor for UV based light emitting diodes (LED). © 2012 The Electrochemical Society. [DOI: 10.1149/2.007302jss] All rights reserved.

Rare-earth doped Ca2SnO4 phosphors were synthesized using a conventional solid state reaction method. The red phosphorescence of Eu(3+) was observed in this system with persistence time. In the as-prepared samples, the doped rare earth ions occupied both Ca and Sn sites in the host lattice. The longest phosphorescent persistence property can be achieved for the Ca2SnO4 phosphors with a 0.1% Eu dopant. Depending on the doped rare earth ions, afterglow emissions of various colors were observed.