Materials Science Forum Vol. 814

Abstract: In this paper, Mn²⁺ doped ZnS (ZnS:Mn) nanoparticles were prepared by co-precipitation method. And then different thickness of TiO₂ and SiO₂ inorganic shell were coated on prepared ZnS:Mn through the hydrolysis reaction of tetrabutyl titanate (TBOT) and tetraethyl orthosilicate (TEOS). ZnS:Mn crystal and core/shell structure were described by X-ray diffraction (XRD) and scanning electron microscope (SEM). Optical property of all ZnS:Mn/XO₂ (X=Ti, Si) nanoparticles were investigated by photoluminescence (PL) spectrometer. The effect of Mn²⁺ concentration and XO₂ (X=Ti, Si) shell thickness on luminescence intensity of ZnS:Mn/XO₂ was studied. The results showed that with TiO₂ and SiO₂ shell thickening, Mn²⁺ emission of ZnS:Mn/XO₂ samples increased first and then decreased. When the thickness of inorganic shell (molar ratio of shell and core amount) reached to 0.5 (TiO₂) and 1.0 (SiO₂), the optimal luminescence intensity was obtained. The emission of ZnS:Mn/TiO₂ and ZnS:Mn/SiO₂ was 2.0 and 1.5 times more in intensity than that of uncoated ZnS: Mn, respectively.

Abstract: A series of red-emitting phosphors, Eu³⁺-doped and Eu³⁺ with Sm³⁺ co-doped Li₂CaSiO₄, were prepared by the combustion method. The phase composition was investigated by XRD, and photoluminescent properties were characterized by fluorescent spectrophotometer. The results show that the diffraction peaks of samples all match well with that of Li₂CaSiO₄ [JCPDS NO. 27-0290]. The excitation spectra consists of the broadband and the sharp lines, which are assigned to the charge transfer band (CTB) of Eu³⁺→O^2– and the typical intra-4f transitions of the Eu³⁺ ions, respectively. The emission spectrum covers the characteristic f-f transitions of Eu³⁺, namely, ⁵D₀→⁷F₁ (596 nm), ⁵D₀→⁷F₂ (620 nm), ⁵D₀→⁷F₃ (657 nm) and ⁵D₀→⁷F₄ (705 nm). The concentration quenching occurs when Eu³⁺ mol fraction equals to 9%. When Eu³⁺and Sm³⁺ were co-doped, the luminous intensity of the emission spectrum was superior to the Eu³⁺ mono-doped, which explains the Sm³⁺ has a sensitization effect for Eu³⁺.

Abstract: Magnesium and its alloys are potential materials in biodegradable hard tissue implants. However, the fast degradation rates in a physiological environment constitute the main limitation for biomedical application. In this work, the NH₄H₂PO₄- KMnO₄ chemical conversion treatment on the surface was used. The morphology and structure of the coating was observed and analyzed by SEM. The electrochemical behavior in Hanks' simulated body fluid of the coated magnesium was systematically investigated. Our results disclose that the corrosion resistance of the P-coated magnesium is significantly improved.

Abstract: Polythiophene(PTP)/microcrystal muscovite conductive composites were prepared by the method of intercalating polymerization via Fe³⁺-H₂O₂ catalytic oxidation system in water. The morphology, structures, electrical conductivity and thermal stability of composites have been studied preliminary. The influence of the different synthesis conditions (temperature, monomer ratio, reaction time) on the conductivity of composite materials was explored. The results of the FTIR and XRD confirmed that thiophene (TP) inserted into the layers of microcrystal muscovite to polymerize and formed intercalation compounds. TG analysis indicated the improved thermostability of composite materials. The PTP/microcrystal muscovite composite made from 2g/ml solution of microcrystal muscovite/TP with reacting for 12h and 15°C showed the highest conductivity 3.56 ×10^-5s/cm^-1.

Abstract: Microarc oxidation (MAO) coatings on ZL108 aluminum alloy were prepared in the silicate-Na₂MoO₄ electrolytes with different current density. The MAO process was studied by measuring the voltage as a function of time. The microstructure, compositions, distribution of element and corrosion resistance of the MAO coatings were investigated by SEM, XRD, EDS, XPS and polarization curve, respectively. With the increasing of current density, the final voltage in the microarc discharge process increased. The results shown that the MAO coatings were mainly composed of mullite, γ-Al₂O₃, Si, little MoO₂ and MoO₃. The micropore size, thickness, compositions, distribution of element of the MAO coatings depended on the current density and the amount of MoO₂ and MoO₃. The corrosion resistance improved as the porosity of the MAO coatings decreasing.

Abstract: The perovskites red phosphors activated by Pr³⁺ were prepared via the combustion method, using citric acid as a fuel and complex agent. The samples were characterized by X-ray powder diffraction and fluorescence spectrophotometry respectively. The effects of calcination temperature and doping Sr²⁺ ion concentration on the phase compositions and luminescence properties were investigated. The CaTiO₃: Pr³⁺ can be obtained with high purity and good crystallinity by the combustion method at different calcination temperatures (750 oC, 850 oC, 900 oC, 950 oC and 1000 oC) for 1 h. The sample obtained at 900 oC exhibits the maximum emission intensity. The crystal structure of the obtained Ca_1-xSr_xTiO₃: Pr³⁺(x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6) changes from perovskite to calcium strontium titanate when x ≥ 0.3. The sample exhibits the maximum red emitting when x = 0.4.

Abstract: The carbon emission and energy consumption of using slag as a secondary raw material in cement production was quantified and analyzed in this study. Moreover, the carbon emission reduction and energy saving potential of slag-based cement (SBC) production were identified based on the comparative analysis between SBC and traditional Portland cement (TPC). The results showed that the carbon emission of SBC is about 6.73%, which was lower than that of TPC. Compared with TPC, the energy consumption of SBC is slightly increased by 2.05%. In addition, it was found that the combustion of coal and the power generation were the main sources for carbon emission in the life cycle of slag utilization, which account for 83.39% and 10.16% of the total carbon emission. Therefore, reducing the consumption of energy and increasing the recovery rate of waste heat in cement production were the most effective methods to improve the environmental performance of SBC. In addition, the improvement potential analysis was carried out for SBC. The results indicated that if the recovery rate of waste heat could reach to that of the international advanced level (15.6%), the carbon emission and energy consumption of SBC would be reduced by about 2.20% and 5.71%, respectively. If the proportion of renewable energy utilizationin power generation increased to that of the average international level, the carbon emission and energy consumption of SBC would be declined by 5.26% and 9.35% respectively.

Abstract: The global warming of cement concrete pavement from raw material extraction to road construction was analyzed by the method of life cycle assessment. The characterization results showed that the procedure of producing material is the most important stage to emit greenhouse gas and it accounts for 98.5% of the global warming potential that caused by the material production and construction stage. For the materials used in different structure layers, surface layer is the biggest impact of greenhouse and accounts for 68.9% of the total impact caused by material used in constructing pavement. Therefore in the future, by using recycled materials or more environmental materials will be a good way to reduce environment impact.

Abstract: The environmental loads are made due to the natural resources and fossil fuels use and pollutants emissions by Chinese thermal power industry. To explore the realistic coal-fired power generation and its denitration strategies, the input and output of coal-fired power generation in China were identified and quantified. The scope of this paper is defined in the boundary of coal-fired electricity generation system all over China. The methodology follows the principal of ISO 14040 and ISO 14044. The functional unit is “1 kWh of electricity generated”. The inventory data of Chinese coal-fired power generation in 2009 without denitration technology applications were measured. The output data include the CO, N₂O, CH₄, CO₂, NOx, PM and SO₂ emissions. NOx emissions are the major contributor of acidification and photochemical in China. To avoid catastrophic environmental damages, the air pollution especially NOx emissions from coal-fired power plants are advised to be cut. For scenario analysis, in the assumption of 100%of selective non-catalytic reduction (SNCR) technology applications, China still has denitration potential. In the coming several decades, the SNCR technology will be decisive for the Chinese coal-fired power industry to reach deeper NOx emission reductions. However, the reduction agents of ammonia and urea usage bring ammonia slip, and extra natural resource and fossils consumption. The urea use also brings extra CO₂ emissions. This limits the applications of SNCR technology to reduce NOx emissions.

Abstract: Ecological design of material is to use the ecological ideology in the material design process, considering the ecological environment problems in the life cycle of material, and scheme out the material which can both meet the demand of human and environment. This paper introduces some ecological design ideas and methods used in the material field, and the latest progress of ecological design and each of their advantages are summarized, the ecological design method of the typical materials is obtained. And finally the present problems to be solved and the future development direction of the ecological design puts forward.