Advanced Materials Research Vols. 887-888

Abstract: It is a facile and efficient way to produce grapheme quantum dots (GQDs) through photo-Fenton reaction. However, the fluorescence of the as-generated GQDs is weak. Here, bright yellow-green fluorescent graphene quantum dots (GQDs) were prepared by post-oxidation of the GQDs with H₂O₂. The fluorescence quantum yields of the post-oxidized GQDs (O-GQDs) increased from 0.08% to 3.3% and the maximum emission wavelength shifted from 450 to 510 nm. The O-GQDs exhibit excitation-independent and pH-dependent photoluminescence behaviors. The increase of the photoluminescence intensity is attributed to the more carbonyl and carboxyl groups after the post-oxidation. The post-oxidation treatment offers a simple pathway to enhance the fluorescence of GQDs.

Abstract: The two-dimensional (2D) assembly of the palladium nanoparticles (Pd NPs) was studied in this work. The cubic Pd NPs were successfully synthesized and assembled on mica and silicon wafer in the dip-coating way. The morphology of the Pd NPs and the topography of the Pd NPs assembly on the substrates were characterized with transmission electron microscopy (TEM) and atomic force microscopy (AFM). In the process of the fabrication, the excess cetyltrimethylammonium bromide (CTAB) was removed with the deposition-redispersion strategy, the UV-vis spectra and zeta-potential of the Pd NPs colloid were measured. It was found that the assembly and AFM characterization of the Pd NPs were affected negatively by the presence of excess CTAB. The hydrophilic property of the substrate is the crucial factor to control the 2D assembly of the Pd NPs. Compared with the washed silicon wafer, mica is ultra-hydrophilic and can attract more Pd NPs.

Abstract: The method of carbon nanotubes by DC-PCVD is analysed. Growth environment of carbon nanotubes is researched with the substrate temperature at 500°C-900°C.The pressure of gas is 60torr,75torr,90torr.It is appropriate when the temperature is 700°C and the pressure is 75torr.Growth characteristic of carbon nanotubes is researched when the concentration of CH4 ranges is 8%-20%.The diameter of carbon nanotubes is uniform when the concentration of CH4 is low.The diameter is not uniform if the concentration is high.

Abstract: In the present study, the heterostructures of ZnO Nanoparticle (NP)/CdS nanowire (NW), SnO₂NP/CdS NW, NiS NP/CdS NW, FeS NP/CdS NW, Ag₂S NP/CdS NW, and Au NP/CdS NW have been successfully fabricated via the two-stage solvothermal process. Field-emission scan electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were adopted to characterize the as-prepared products. The optical properties of the as-obtained heterostructures were separately investigated. New insights into understanding and controlling the synthesis of different NW heterostructures are demonstrated in the reliable solvothermal route. We demonstrate that CdS NWs synthesized for 2h are the bifunctional mediator acting as catalyst or active spot for the growth of NW heterostructures Furthermore, understanding and controlling this phenomenon is a great asset for the realization of the formation mechanism of the NW heterostructures and opens up new ways toward for construction of other semiconductor heterostructures with novel properties.

Abstract: The microsphere Bi₂WO₆ has been synthesized by a facile hydrothermal method by using Bi (NO₃)₃5H₂O, H₄₀N₁₀O₄₁W₁₂5H₂O and CO(NH₂)₂(urea) as the starting materials. The as-synthesized Bi₂WO₆ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM),BET and UV-vis absorption spectroscopy. The visible-light-responsive photocatalytic activity of Bi₂WO₆ microspheres was evaluated by the photo-degradation of RhB under Xe lamp irradiation. The degradation is up to 96% in 3h. The results show that microsphere Bi₂WO₆ exhibited excellent photocatalytic activity. The reasons for the high photocatalytic activity have been discussed carefully.

Abstract: Inclusion’s source and character in different T[ content are studied in the paper, molten slag and refractory material that leave in steel are also calculated. Inclusion in steel are principally come from deoxidation, accompany with the decrease of T[ content, influence of molten slag and refractory materials to inclusions are getting more and more serials. Inclusions which come from molten slag and refractory material are 88.9%, 24.6% and 18.1% defenetly. Great influence on non steady large inclusions in T[ steel, when the mold level fluctuation is large, almost 100% of inclusions in steel have slag inclusion of covering slag. When tundish liquid level fluctuation is large, about 30%~60% inclusions in steel have tundish slag.

Abstract: Influence on the transient casting of large inclusions in steel were studied by means of tracer method, kinds of steel large inclusions content in transient casting is 1.5 times ~8 times to the steady casting, large inclusions principal from crystallizer mold powder entrapment, then the tundish slag and the ladle slag. Slag and refractory has a certain influence on high quality steel. Reducing fluctuations caused by transient casting is the key to improve the quality of the steel.

Abstract: As the competition for steel department becoming fierce, the custom bring forward more district requirement. When deal with the quality dissidence, jingtang company find many dissidence is result in elongation does not meet the set point, bring too much economic damnify. So the author analyzed the technology of elongation and the control system, tested the stiffness of the tempermill, finally optimized the control system and the minimum roll force and the tension of temper according the analysis result, find a property technology for this kind of strip to product.

Abstract: High temperature tensile tests of novel developed Nb-microalloyed weathering steels were carried out with a constant true strain rate of 0.001/s at 650°C-1300°C using Gleeble3500 thermo-mechanical simulator. The tensile strength (TS) and reduction in area (RA) were calculated afterwards to obtain hot ductility curve and hot strength curve of the steel. The hot ductility behaviors were studied in detail under optical microscope (OM), scanning electron microscope (SEM) and transition electron microscope (TEM). The third brittle zone of the studied steels was between 650°C-800°C. SEM fractographs and microstructures of the tensile specimen showed that the occurrence of the third brittle zone was mainly related to the formation of pro-eutectoid ferrite film along the prior austenite grain boundaries, and secondly to the precipitation of second phases. Therefore, it was recommended that the straightening temperature of the studied steel after casting should be kept over 800°C to get crack free continuous casting (CC) slabs.