Key Engineering Materials Vol. 633

Abstract: Using the industrial limestone, fly ash and pure chemical reagents as raw materials, the blast furnace slag was prepared in the simulation condition of the actual slag-making process by three different cooling ways, including air cooling, water cooling and liquid nitrogen cooling. Combined with different test methods such as XRD, SEM, IR, the influence of cooling ways on the structure and hydraulic activity of blast furnace slag was studied in the present in investigation. The relationship between glass content, compressive strength and the phase compositions of blast furnace slag has been obtained. The results showed that, the glass content of water cooling slag or liquid nitrogen cooling slag was slightly higher than that of air cooling slag, there was obviously gehlenite crystal phase in air cooling slag. The 7d and 28d compressive strength of three slags did not present positive correlation with vitreous content, the sequence of 28d compressive strength of three slags was water cooling slag > air cooling slag > liquid nitrogen cooling slag. SEM observation found that crystallization phases in water cooling slag had a small grain and uniform distribution, this kind of structure was advantageous to the latter hydration reaction and strength development of blast furnace slag.

Abstract: Granulated blast furnace slag (GBFS) is a by-product of manufacturing iron. Samples of GBFS with different ratio of SiO₂/Al₂O₃ were prepared by simulating the actual process of GBFS in laboratory. This study investigated the influence of SiO₂/Al₂O₃ content on structure and hydration activity of GBFS which were characterized by X-ray fluorescence (XRF), powder X-ray diffraction (XRD), infrared radiation (IR) and mechanical testing. It is found that the vitreous content of each sample is above 97% and the hydration activity indexes of 7d and 28d of samples significantly decrease with the increase of SiO₂/Al₂O₃ ratio. The IR characteristic absorption spectrum shows that the silicates mainly exist in [SiO₄]-tetrahedra and the aluminum atoms are in different coordination states and the bonding strengths rise with the increase of SiO₂/Al₂O₃ ratio.

Abstract: Specimens were prepared using iron-rich magnesia (3~1 mm、≤1 mm) and high purity magnesia (≤0.088 mm) as the main starting materials, adding tabular alumina at different size (3~2、2~1、≤1 mm) and content:3%、6%、9%、12%、15% to discover the influence of tabular alumina on sample performance. Phase composition and microstructure were also analyzed. The results show that specimen with content of 6% of corundum possessed the best comprehensive performance:apparent porosity 17%, bulk density 2.95 g·cm^-3, cold crushing strength 74 MPa, refractoriness under load 1700 °C, heat shock resistance of up to 18 times. The formations of magnesium aluminate spinel and hercynite solid solution were enhanced by Fe ion at high temperatures in the iron-rich magnesia-corundum system at the presence of iron oxides, which are able to largely dissolved in periclase.

Abstract: The new mullite-SiC bricks were prepared by mullite homogenized grogs to substituted the bauxite clinkers (Al₂O₃ content is 85% or 88%) as raw materials. In this paper, the physico-chemical properties and wear resistance of the new mullite-SiC bricks were studied by comparing with the ordinary mullite-SiC bricks produced by using bauxite clinkers as raw materials. The result shows that the new mullite-SiC bricks have low apparent porosity and bulk density, high compressive strength and refractoriness under load, excellent wear resistance. The mullite homogenized grogs can substitute the bauxite clinkers as materials to produce mullite-SiC bricks and improve the properties of the bricks.

Abstract: A red light-emitting phosphor of SrMoO₄: Pr³⁺ was synthesized by a convenient high-temperature solid-state reaction method. The structures, morphologies and optical properties of as-prepared products were characterized by X-ray diffraction (XRD), transmission electron microscope (FESEM) and photoluminescent (PL). A strong red emission centered at 645 nm corresponding to the 3P₀→3F₂ transition of Pr³⁺ is observed under 430–500 nm excitated. In addition, it has been found that M⁺ (M⁺ = Li⁺, Na⁺ or K⁺) codoped SrMoO₄: Pr³⁺ phosphors could lead to a remarkable increase of photoluminescence. Luminous intensity was the highest when doping Na⁺ ions. The influence of the sintering temperature on the luminescence properties of the phosphors is also discussed. The optimum sintering temperature was 900°C. The average particle size was about 2~4 μm. Thus, it is a promising material for solid-state lighting based on GaN light-emitting diode (LED).

Abstract: Gd2O3-doped bismuth titanate (Bi4-xGdxTi3O12: BGT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Gd-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675 °C to lower temperature and a improvement in dielectric property. The experimental results indicated that Gd doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BGT film with x=0.75 were 28 μC/cm2 and 65 kV/cm, respectively.

Abstract: The electrical properties of Gd-doped bismuth titanate Bi_4-xGd_xTi₃O₁₂ (BGT) ceramics prepared by a conventional electroceramic technique were investigated. XRD analyses revealed Bi-layered perovskite structure in all samples. SEM micrographs showed randomly oriented and plate-like morphology. For the ceramics with x=0.25 and 1.0 the current-voltage characteristics exhibited negative differential resistance behaviors and their P-E hysteresis loops were characterized by large leakage current, whereas for the ceramics with x=0.5 and 0.75 the current-voltage characteristics showed simple ohmic behaviors and their P-E hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( P_r ) and coercive field (E_c) of the BGT ceramic with x=0.8 were above 16μC/cm² and 70KV/cm , respectively.

Abstract: The electrical properties of Tb₂O₃-doped bismuth titanate,Bi_4-xTb_xTi₃O₁₂ (BTT) ceramics prepared by a conventional electroceramic technique have been investigated. XRD analyses indicted Bi-layered perovskite structure in all samples, and revealed that Bi ions were only substituted near the Ti-O octahedron layers by Tb ions. SEM micrographs show randomly oriented and plate-like morphology. The remanent polarization ( P_r ) and coercive field ( E_c ) of the BTT ceramics with x=0.75 were above 16μC/cm² and 75KV/cm, respectively. The large value of remanent polarization and low coercive field of Tb-doped bismuth titanate ceramics promote these materials to potential applications.

Abstract: Cd_1-xMn_xTe (CdMnTe) can be a good candidate for gamma and X-ray detection because of its wide band-gap, high resistivity, and good electro-transport properties. Polycrystalline CdMnTe films were grown by closed-space sublimation method on glasses at different substrate temperatures. In this paper, substrate temperature dependent surface morphology, chemical composition, structural and electrical properties of CdMnTe films are investigated systematically.

Abstract: The study of dye-sensitized solar cells (DSCs) based on nanocrystalline films of high band gap semiconductors is a progressive field of research that is being carried out by scientists in a wide range of laboratories. To improve the conversion efficiency of the DSCs, the SnO₂ nanorots photocurrent is prepared via the hydrothermal method, and characterized by XRD, FESEM, BET and Absorption spectrum. Though analysis the results, the conclusion is shown the pure SnO₂ is preparation, the SnO₂ nanocrystalline both shows the single phase that SnO₂ from the sule solution to kalin solution. The prepared SnO₂ nanocrystalline under pH=3 shows the particle-shape crystalline, the surface area of SnO₂ nanocrystalline is 86.3412m²/g. The prepared SnO₂ nanocrystalline under pH=7 shows the short rod-shape crystalline, the surface area of SnO₂ nanocrystalline is 58.3408m²/g. The absorbance of SnO₂ nanocrystalline shows the strong absorption in the ultraviolet ray range, the absorbance of synthesized SnO₂ nanocrystalline under pH=11 shows the highest value.