Materials Science Forum Vols. 743-744

Abstract: This study attempted to estimate the environmental performance of poly (propylene carbonate, PPC) in the whole life cycle. The life cycle is from raw materials, energy acquisition, manufacture, transportation, to the final disposal, sequentially. The environment impacts of these phases are assessed by the method of Life Cycle Assessment (LCA) to identify key aspects of environmental loads involving global warming, non-renewable resource consumption, and acidification effects and so on. Moreover, a comparative study due to manufacturing of PPC in its whole life cycle was taken to reveal which stage would make the most environmental load.

Abstract: TiO₂@CNTs nanocomposite was synthetized by a hydrothermal method at 453 K, using titanium tetrachloride as a precursor and nitrified CNTs as a support. The crystal phase, morphology, microstructure and element distribution of the sample were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (TEM), and scanning transmission electron microscopy (STEM-Mapping). The photocatalytic activity of the sample was measured by degrading methyl orange under UV illumination. The results showed that the titania particles in the shape of regular polygon decorate on the outer surface of CNTs evenly, and their sizes were about 7-20 nm. Moreover, photocatalytic activity of the nanocomposite was better than that of P25 Degussa and nitrated CNTs followed the apparent pseudo-first-order rate law. These results point out that synergistic effect exists between the titania and the carbon nanotubes in the nanocomposite.

Abstract: The photodegradation of organic pollutants by TiO₂ has previously been shown to be efficient, but the TiO₂ particles are typically so fine that they are easily washed away. This problem was solved by forming a complex between TiO₂ and bentonite. Four different photodegradation conditions (i.e., no catalyst, addition of 3 bentonite, addition of 1 TiO₂, and addition of 3 TiO₂-bentonite) were investigated for their degradation efficiencies of 20 mg/l sodium dodecyl benzene sulfonate (SDBS) under ultraviolet light for 6 h. The titanium content of 1 titanium oxide was equal to that of the 3 Ti-bentonite. The results showed that, under the four above conditions, 36.7%, 25.9%, 96.7%, and 99.3%, respectively, of SDBS were degraded in the aqueous solutions. The latter two conditions degraded SDBS more efficiently than the former two conditions. The TiO₂-bentonite complex possessed more advantages than TiO₂ or bentonite alone, making the bentonite an appropriate carrier for TiO₂.

Abstract: Pure TiO₂, Ce-doped and Ce/Si-codoped TiO₂ nanoparticles with different Ce contents were synthesized by using a sol-gel-hydrothermal method. The as-synthesized samples were annealed at 400 °C. Their crystallization was investigated by Raman spectroscope. The result showed that Ce-doping and Ce-Si codoping decreased the crystallization. The interfacial and fractal properties were investigated by synchrotron radiation small angle X-ray scattering (SAXS). The results indicated that Ce-doping induced the Porod negative deviation, and the fractal properties showed TiO₂ nanoparticles codoped by Ce-Si were rougher than these of the pure TiO₂ and Ce-doped TiO₂. This rough surface of the nanoparticles was helpful to improve the photocatalytic activity.

Abstract: An efficient α-SiW₁₁Ti/PANI/TiO₂ nanocomposite photocatalyst was prepared by a In-stiu polymerization method. (NH₄)₂S₂O₈ was used as an oxidant to form polyaniline-wrapped TiO₂ particles and then by an electrostatic assembly of α-SiW₁₁Ti. The α-SiW₁₁Ti/PANI/TiO₂ nanocomposite were characterized by UV-visible absorption spectrum (UV-Vis), Fourier transformation infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The photocatalytic activity in degradation of malachite green on the α-SiW₁₁Ti/PANI /TiO₂ was carried out in an aqueous solution. The results show that the sensitizing effect of PANI can improve the light response of TiO₂ and enhance the separation efficiency of electron and hole pairs, which in turn promotes the photocatalytic activity of the composites. This novel photocatalyst exhibits high photocatalytic activity to decompose malachite green under 30 W ultraviolet light irradiation. The malachite green was degraded by 97.53% after 90 min irradiation on the α-SiW₁₁Ti/PANI/TiO₂ nanocomposite, which was better than that of Degussa P25 (TiO₂) and PANI/TiO₂.

Abstract: In order to improve the separation efficiency and the circular utilization ratio of the catalyst, the Fe-doped nanotitanium and nanotitanium supported on Fe₂O₃ carrier was prepared by hydrothermal method. The tetra-butyl titanate and ethanol were used as starting materials to prepare nanotitanium. The results of Fe-doped nanotitanium showed that the doping of iron changed the nanotitanium crystal and crystal morphology. No matter UV-light or mercury lamp 577 nm irradiation, the samples with 0.5 mM Fe addition showed the highest photo catalytic activity, with degradation rate of methyl blue above 95%. The structure, photo catalytic activity and magnetic properties analysis showed that the magnetic nanotitanium met the purpose of separation between the catalyst and reaction solution. The photo catalytic activity of nanotitanium supported on Fe₂O₃ carrier has respond to visible light. With mercury lamp 577 nm as irradiation source, degradation rate of methylene blue light could reach 63.40%.

Abstract: Titania powder was prepared by a sol-gel method and heat-treatment (HT). The morphology and structure of the titania powder were characterized by X-ray diffraction (XRD), differential thermal analysis, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of powder was investigated using methyl orange as target compound. Colour changing of powder was due to colour centers form. Under visible light, yellow powder showed the better photocatalytic activity than P25 powder and its visible light response was expanded. Preparation of yellow powder lowered conventional calcinations temperature obviously.

Abstract: Mo thin films were prepared by Mid-Frequency twin target magnetron sputtering as the high reflectivity coating in high temperature solar selective coating. The structure and optical properties of the coatings were studied by X-ray diffraction, scanning electron microscopy and Fourier Transform Infrared Spectrometer and spectrophotometer, the optical constants were inversely calculated by Handley equation. The highest infrared reflectivity of 94% reached at the bias voltage of-150 V and sputtering current 12A of the Mo cathode source, which satisfy the requirement for low thermal emittance solar selective coating applications. The thin films with body centered cubic structure grew along the (110) surface as column crystal, optical constants of Mo thin film were similar with bulk Mo. The thermal emittance of the infrared high reflectance Mo based selective absorber coating can control in 0.15 (400).

Abstract: Upgraded metallurgical grade (UMG) silicon has been researched both on the purification methods and its material properties for years, indicating that it is the most promising choice as low-cost feedstock for photovoltaics. In this work, UMG multi-crystalline silicon (mc-Si) prepared by cold crucible refining and electron beam melting was investigated. Solar cells based on such silicon wafers were fabricated in a 156 x 156 mm² production line and their photovoltaic properties were characterized. Compared with the conventional mc-Si solar cells fabricated in the same commercial production line, the UMG mc-Si solar cells with two busbars presented higher average open circuit voltage (V_oc) and average fill factor (FF), which were 628 mV and 78.6 % separately. Although the UMG mc-Si solar cells showed a lower shot-circuit current density (J_sc) of 32.7 A/cm² in the average and an early reverse breakdown voltage at around 11 V which was due to higher impurities content. The average conversion efficiency of the UMG mc-Si solar cells reached 16.14 %, and the highest conversion efficiency was up to 16.31 %. In addition, the UMG mc-Si solar cells presented relatively low light induced degradation (LID) due to the material properties. Consequently, in consideration of low cost, our UMG mc-Si solar cells substantially met the requirements of commercial manufacturing and had a great potential application for photovoltaic industry.

Abstract: Activation energy is an important parameter which determines thermal stability of solar selective absorbing coating. In this investigation, a new performance criterion (PC) was defined for solar selective coating according to our modified equation of photo-thermal conversion. Then the activation energy of Cu/stainless steel (SS)-AlN/SiAlO_x solar selective absorbing coating was measured. Cu/SS-AlN/SiAlO_x tandem films were deposited by magnetron sputtering. Accelerated ageing tests were performed on the coating at 500°C and 550°C, under the atmosphere, calculating PC from the reflectance spectrum and measuring the failure time. According to Arrhenius equation, the activation energy and the equivalent life span of Cu/SS-AlN/SiAlO_x tandem film at 400°C were determined to be about 187.4kJ/mol and more than 16260 hours, respectively.