Key Engineering Materials Vol. 633

Abstract: Super-grade bauxite, pure silicon carbide, andalusite and metal silicon were used as the raw materials to produce plastic phase mullite-SiC bricks. By analysis of the microstructure, physical and chemical properties, it proves that the introduction of metal plastic phase can improve the properties of bricks, such as lower porosity, higher cold crush strength, and wearing resistance. It also can improve the toughness, and effectively relieve the thermal and mechanical stress when using in cement kilns. By analysis of the comparison with MA spinel bricks and ordinary mullite-SiC bricks, the plastic phase mullite-SiC bricks have good thermal shock resistance and lower thermal conductivity. The result shows that the bricks can replace MA spinel bricks using in the transition zone of cement kilns and realizes the aim of saving energy and a long service life.

Abstract: LTCC films constrained by rigid substrate were sintered at different temperatures ranging from 760 °C to 800 °C. An optical dilatometer together with a rocking arm was employed to record sintering strains of the constrained films during the sintering process. The densification behavior of constrained films was systematically studied through the measured sintering strains by comparing with that of freely sintered films. For the constrained films, the final density was smaller and the activation energy for the densification was larger than that of the freely sintered ones. Moreover, anisotropic microstructure was induced by the tensile stress.

Abstract: Sulfate-ion pillared layered hydroxide of Eu₂(OH)₄SO₄·nH₂O (n~2, SO₄^2--LEuH) was synthesized through controlled hydrothermal reaction, and the phase evolution of which upon calcination in the air and hydrogen was studied in detail. It was found that annealing in the air produced orthorhombic Eu₂O₂SO₄ in the temperature range of 300-1000 °C while in flowing H₂ hexagonal Eu₂O₂S was resulted in the 600-1000 °C range. Strong red emissions were found at 621 nm for the SO₄^2--LEuH and 627 nm for Eu₂O₂S under excitation at 396 nm (the ⁷F₀-⁵L₆ transition of Eu³⁺). Improved luminescence intensity was also observed for the Eu₂O₂S powder calcined at a higher temperature.

Abstract: Zinc acetate dehydrate and Graphene oxide (GO) were employed as raw materials, the ZnO/Graphene composites were simply and quickly synthesized by solvothermal reaction at 180°C for 12 h. The phase structure and morphologies of the as-obtained composites were characterized and observed by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Using RhB solution simulated dye wastewater, the composites’ photo-catalytic performance were preliminary tested and observed with the visible light irradiation. The results indicated that the concentrations of zinc acetate and the mass ratio of zinc acetate dihydratio and graphene oxide all had an impact on the photo-degradation rate. The photo-degradation rate of the composites prepared with the concentrations of zinc acetate of 0.01 mol/L was higher than that of zinc acetate of 0.001 mol/L. The mass ratio of zinc acetate dehydratio and graphene oxide of 4:1 was higher than that of 8:1.

Abstract: The surface morphology of quartz glass etched in HF acid is influenced by many factors, such as the quality of polishing, types of the quartz glasses, metal ion in HF acid, etc. This paper conducted an analysis on these factors and tried to make improvements. Meanwhile, this experiment approved of the model of both destructive layer and the varying of closed micro-cracks in the process of etching. Besides, the changing law of both ditch-like and pit-like flaws was investigated in this experiment, and conclusions could be drawn as follows: at the concave curvature, the bigger the radius of curvature is, the faster the etching will be; The etching rate with protruding curvature is higher than that of concave curvature; The etching rate with concave curvature is lower than that on the plane surface.

Abstract: Polystyrene (PS) microspheres were prepared by dispersion polymerization method and using PS microspheres as pore former porous hydroxylapatite (HA) was prepared by Liquid phase precipitation method. The phase constituent was analyzed by X-ray diffraction(XRD) and by Fourier transform infrared(FTIR) and the microstructure was observed under scanning electron microscopy (SEM), field emission scanning electron microscope (FE-SEM) and transmission electron microscopy (TEM). The results showed that the prepared porous HA was of high purity and their pores were evenly distributed, with pore about 200nm in diameter. PS microspheres were probably the most economic and environmental pore-forming materials.

Abstract: The performance and phase behavior of Quartz - Aluminum Matrix Composites at different temperatures were studied. Quartz aluminum matrix composites were prepared by powder metallurgy method. At the temperature that was less than 660.4°C(the melting point of aluminum), a portion of quartz was happened decomposition and revivification to silicon, most aluminum still existed in the form of metal aluminum. All quartz were happened at the temperature that was higher than 660.4°C. When the temperature is 700°C, the compressive strength of S5(added 40% quartz) is up to 46.02MP. The higher the value of compressive strength was, the less the amount of quartz were happened decomposition. At the temperature more than the melting point of aluminum, Quartz was revivification to silicon, aluminum is oxidized to Al₂O₃. When the amount of silica exceeded 10%, the mechanical properties of composites declined consequently.

Abstract: Catalysts of Mn/TiO₂ and Mn-Ce /TiO₂ prepared by co-precipitation method for low temperature selective catalytic reduction (SCR) of NO with NH₃ were investigated in this study. The experimental results showed that co-precipitation method after improvement, the NO conversion of Mn-Ce/TiO₂ catalyst increased sharply. Meanwhile, the addition of cerium has significant effects on the catalytic activity. Characterizations of catalysts were carried out by XRD, BET and H₂-TPR. The characterized results indicated that co-precipitation method after improvement, in temperature windows 150 to 300 °C, showed higher NOx conversion.

Abstract: A novel approach of reusing kerf loss wastes in preparation of β-SiC/Si₂N₂O bonded SiC refractory has been proposed. Thermodynamic analysis was conducted to prove the theoretical feasibility. β-SiC/Si₂N₂O bonded SiC refractory was successfully prepared at 1723K by adding kerf loss wastes replacing partial industrial SiC and Si powder on the condition of being buried with carbon. The β-SiC/Si₂N₂O bonded SiC refractory exhibited low porosity and excellent mechanical properties. Both Silicon powder in kerf loss wastes and industrial silicon powder formed β-SiC, Si₂N₂O and a small amount of SiO₂. The approach proposed is beneficial for reducing the cost of preparation of SiC-based refractory as well as protecting the environment.

Abstract: This paper presences the influence of coarse aggregate-space coefficient on the rheological properties of self-compacting concrete (SCC). The results indicate that coarse aggregate-space coefficient has significant influence on slump flow and V-funnel flow time of SCC, when the maximum aggregate particle size is 16mm and the volume ratio of sand and motor is 0.43, meanwhile water binder ratio is 0.38. The higher the coarse aggregate-space coefficient, the lager the slump flow, the shorter the V-funnel flow time. The range of coarse aggregate-space coefficient of SCC is suitable for 1.31~1.58 under the condition of the paper. The suitable range can guarantee excellent rheological properties and stability of SCC mixture. There is little effect of coarse aggregate-space coefficient on compressive strength in this paper tests.