Advanced Materials Research Vol. 772

Abstract: Pyramidal surface is commonly used as an antireflection structure. The weighted reflectance averaged by the AM 1.5 G spectrum is about 14%. In the photovoltaic field, lowering the surface reflectivity is an important approach to improve the conversion efficiency. Black silicon surface with low reflectivity is benefit of solar cells. But conversion efficiency of black silicon solar cell is still low due to the severe surface recombination. In this paper, shallower black silicon layer was formed on the pyramidal surface. For the sample etched 1 min, the weighted reflectance is only 13.20%, and the pyramidal one is 14.10%. The layer would not deteriorate the material. Lifetime of the substrates after high temperature phosphorous diffusion is 13.35 μs higher than the pyramidal one. The mean sheet resistance is nearly the same between the pyramidal surface and the etched pyramidal surface.

Abstract: The self-organized hollow TiO₂ hemisphere with a height of 130 nm and a diameter of 200 nm was formed. Highly ordered TiO₂ nanotube arrays of 200-nm pore diameter and 700-nm length were grown perpendicular to a FTO substrate by infiltrating the alumina pores with Ti (OC₃H₇)₄ which was subsequently converted into anatase TiO₂. The structure was treated with TiCl₄ to enhance the photogenerated current and then integrated into the DSSC using a commercially available ruthenium-based dye. The dye-sensitized solar cell using self-organized hollow TiO₂ hemispheres under porous alumina with TiO₂ nanotubes inside as the working electrode generated a photocurrent of 5.00 mA/cm², an open-circuit voltage of 0.58 V and yielding a power conversion efficiency 1.77 times the conventional nanoparticle-based DSSC.

Abstract: TiO₂ nanotube arrays (TNAs) modified by CuO (CuO-TNAs) catalysts were prepared by an impregnating-calcinating method using the electrochemically prepared TNAs and Cu (NO₃)₂ as precursors and were characterized by scanning electron microscope, transmission electron microscopy, X-ray diffraction spectroscopy and UV-visible spectroscopy. The electrocatalytic properties of the CuO-TNAs samples for hydrogen evolution reaction (HER) were investigated by linear sweep curves, electrochemical impedance spectrum and current-time curves. The results showed that the electrocatalytic activity of TNAs for hydrogen evolution reaction (HER) was significantly enhanced by CuO modification, and the electrocatalytic activity of CuO-TNAs catalysts could be further promoted by visible-light illumination. The combination of visible-light irradiation with applying a controlled potential may provide new insight into enhancing the performances of the cathode for hydrogen evolution reaction.

Abstract: Pd (en)₂Cl₂ can be intercalated into graphite oxide layers with high efficiency. The Pd (en)₂²⁺ intercalated graphite oxide was firstly synthesized by mixture reaction of Pd (en)₂Cl₂ and graphite oxide, then it was reduced in solution with NaBH₄ and thereafter the graphene/Pd nanosized particle composites were obtained. The graphene composites were characterized by XRD, FE-SEM, TEM, ICP and N₂ adsorption tests and their H₂ storage was also measured. The results show that the composites contain a large amount of Pd and have a regular mesoporous structure, and Pd particles with a diameter of 2-6 nm are evenly dispersed between graphene sheets and pillar the graphene sheets. The BET surface area of the composites is 230 m²/g and their H₂ storage reaches 3.4 wt.% at 77K and 0.11 MPa.

Abstract: Object of researches is continuous laser radiation sources on the mineral samples, the objects of alluvial layers, which contain gold, not extracted by gravitational methods. The formation of different structural surfaces of gold is established, general laws governing agglomeration and concentration of sub-micron gold are revealed.

Abstract: Two kinds of supported iron nanoparticles by activated carbon/carbon nanotubes were synthesized under ambient condition in this study. And their performance for pentachlorophenol (PCP) removal in water was examined. The SEM images showed that the nanoparticles supported by carbon nanotubes (Fe-CNTs) were of better dispersibility and smaller particle size than that by activated carbon (Fe-C). And the iron content in both of Fe-CNTs and Fe-C system measured by EDS was similar to each other. But the removal rate of PCP in the former system was obviously lower than the latter. It might be due to the more excellent adsorption capacity of activated carbon. And another main reason could be the reduction of adsorption sites due to the occupation of iron nanoparticles. The removal of PCP from the solution was the result of both of the activated carbon/carbon nanotubes adsorption and iron degradation. And the adsorption process was prior to the degradation by iron nanoparticles.

Abstract: Titanium dioxide (TiO₂) nanoparticles were successfully synthesised by hydrothermal method using TiO₂ microparticle powder (Merck) as precursor. TiO₂ microparticles powder (~160 nm) was mixed with 10 M NaOH and treated hydrothermally at 150 °C and 2 MPa pressure in autoclave for 24 hours. After hydrothermal reaction was completed, the sample was washed, dried and heated at 500 °C for 2 hours to produce TiO₂ nanoparticles. The synthesised nanoparticles were characterized using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and raman spectroscopy. UV-Vis DRS was used to determine the band gap energy. Field emissions and transmissions electron microscopy images revealed that nanoparticles obtained was about 14 nm. X-ray diffraction patterns showed that TiO₂ nanoparticles were anatase phase (tetragonal). The band gap energy of TiO₂ nanoparticles was determined to be 3.32 eV.

Abstract: TiO₂/Co²⁺ composite nanofibers were prepared by using the electrospun fibers of PVP/ Ti (OiPr)₄/Co (NO₃)₂ composite as precursor, and through calcination treatment. The chemical components, structures and morphology were characterized by TGA, FT-IR, XRD, SEM, respectively. The photocatalytic activities of the catalysts were investigated by photocatalystic degradation of Rhodamine B under visible-light irradiation. It was found that the TiO₂/Co²⁺ composite nanofibers calcined at 600 °C which was the anatase phase, showed higher photocatalytic activities than those calcined at other two temperatures. This result was expected as a new morphology of photocatalysts to degrade the organic pollutants in the sun.

Abstract: The KH-550 was modified by KH-560, and a new surfactant was got, which was used to modify nanosilicon carbide. Series of modified polyurethane elastomers (PUE) were prepared with 2,4-toluene diisosocyanate (TDI), poly (propylene glycol)(PPG-2000), modified nanosilicon carbide, carbon nanofibers and 3,3'-4,4'-dianino-diphenymethane (MOCA). The influence of different amount of filler on the mechanical properties, wear resistance of composite materials was investigated. The dispersion degree of nanofiller in matrix was analysised by SEM. The results showed that the comprehensive properties of composite had been greatly improved.

Abstract: Stone Wales (SW) defect is one type of topological defect on the CNT, in this study we performed first principles calculations of SW defects in armchair edge (5,5) carbon nanotube (CNT) by the density functional theory (DFT). Two different defects were studied such as longitudinal and circumference types. Our calculation results show that a longitudinal SW defect is more stable than circumference SW defect. However barrier energy as parameter to control the SW defect in CNT was studied, in calculation we applied Nudge Elastic Band (NEB) method to find minimum energy path (MEP) and barrier energy for SW defect transitions. The result shows that barrier energy of circumference SW defect is lower than another one. We also found that in the case of circumference SW defect, armchair edge (5,5) CNT become semiconductor with the band gap of 0.0544 eV.