Advanced Materials Research Vol. 968

Abstract: Taking aluminum sulfate and urea as the raw materials produce α-Al₂O₃ in different shapes by employing the hydrothermal-pyrolysis method. The study analyzes the characterization of the products by XRD and SEM, and explores the effects exerted by factors like time span of the hydrothermal reaction and additives such as PEG on the products’ morphology. The results indicate as follows: after 6 hours’ hydrothermal reaction in the 120°C water, with the aluminum sulfate and urea as the raw materials, spherical α-Al₂O₃ can be obtained through calcination at 1200°C. In the same condition but taking PEG 2000 as additives, tabular-shaped α-Al₂O₃ can be produced respectively by controlling the reaction time. This paper explores the formulation mechanism of α-Al₂O₃ in different shapes and the result shows that the growing environment of the crystal nucleus plays a vital role in the formation of the α-Al₂O₃’s shape.

Abstract: In order to study the mechanics properties to of concrete columns with embedded steel, analysis models of SRC columns are established by using finite element software ABAQUS. Firstly, in order to validate the rationality of the analytical model, the test specimens are modeled, the results obtained from the finite element and experimental analyses are compared to each other, it is found that the finite element behavior indicates a good agreement with the experimental behavior. Furthermore, the ductility and ultimate capacity of SRC columns are studied with the changes of steel bone ratio and the axial compressive ratio. Analytical results demonstrate that embedded steel improves the ductility of SRC columns with large axial compressive ratio and steel bone ratios have obvious effect on ductility and ultimate capacity of SRC columns. The study results have some value on the design and application of the SRC columns.

Abstract: Transition metal carbonyls are novel catalysts.This study examined the removal effect of COS over Fe2(CO)9 at atmosphere pressure compared with the removal of CS2 over Fe2(CO)9 at atmosphere pressure.By experiment contrast analysis,the removal effect of COS better than the removal effect of CS2. It shows that the existence of CO without producing competition.The removal effect of COS basically maintain the level of 60%~80% is good at atmosphere pressure.Then analyzing of Reaction mechanism, there are three kinds the interaction between Fe2(CO)9 and COS at atmosphere pressure are listed.There is every reason to believe that Fe2(CO)9 can make COS activation.

Abstract: The effect of cooling condition on the chromium elution from stainless steel slags was investigated. The experiments were carried out in a muffle furnace and an induction furnace, and the leaching test was according to the standard procedure, prEN12457-2. The results show that the oxidation atmosphere enhances the elution of chromium, and the dissolving amount of chromium increases with the increase of temperature. The reducing atmosphere could restrain the elution of chromium. Therefore, it is better to take advantage of the neutral or reductive atmosphere for slag cooling in order to reduce the elution of chromium from stainless steel slag.

Abstract: This paper aims at doing research on the variation of volume fraction of precipitation. And Avrami empirical equation characterizing the relationship between transformation ratios and ageing time is established. This research was carried out by measuring the electric conductivity of Cu-Ni-Be wedge copper alloy after ageing treatment, and analyzing the relationship between electric conductivity and volume fraction of precipitations. Consequently, the equation between electric conductivity and the ageing time is fixed. Then S-curves of the dynamics of phase dynamics of phase transformation and C-curves of isothermal transformation for the Cu-Ni-Be wedge copper alloy are derived.

Abstract: Crystallization kinetics experiment of calcium sulfate dehydrates, which is prepared by bittern under 40oC and 200r/min conditions, is carried out. According to the results of the experimental data, the relationship of nucleus particle-number density n⁰ and crystal growth rate G with the residence time is summarized. Also, the average diameter of gypsum crystal is decreasing with the residence time increase. Meanwhile, the crystallization kinetics formula is derived to be: B⁰=3.20×10⁵G^0.47.

Abstract: The quality of the kaolin is always measured by iron contents since this element gives undesirable reddish color which limits the usage of this type of minerals. Reducing the iron contents to increase the value of kaolin by bleaching process is investigated. The effects of factors which can improve the whiteness of kaolin have been studied. The dosage of sodium dithionite, pH value, solid-to-liquid ratio and reaction time were chose as factors based on mono-factor experimental results. Orthogonal experiments were carried out and the optimum processing conditions of the reductive bleaching were obtained as the dosage of sodium dithionite 3%, pH 2, solid-to-liquid ratio 1:3 and reaction time 45min. After bleaching process described above, we obtained a great improvement in the whiteness from 69.93% to 81.31% and a decrease of Fe₂O₃ content from 0.52% to 0.40% of the kaolin.

Abstract: Effects of Gas Induce Semi Solid (GISS) on shrinkage porosity of 7075 aluminum alloy were investigated. Initial solid fractions were controlled by rheocasting time at 5, 10 and 15 seconds and 4 and 6 bar of gas pressure. The results showed that the initial solid fractions were increased by increasing rheocasting time and gas pressure. As for the shrinkage, values of the GISS process samples were lower than those of the conventional process samples. In addition, the shrinkage areas of semi solid samples were decreased by increasing the initial solid fractions. The microstructure of semi solid samples was shown to be uniform globular grains along the samples.

Abstract: A new process of making steel by direct alloying with molybdenum oxides has been regarded in years. The characteristic of the new process is by using of the cheaper molybdenum oxides powder as alloy agent which can improve the flexibility of choosing main raw materials. The implementation of the process can reduce the production cost, protect environment and improve the economic profits and social benefits. In this study, an industrial experiment for direct alloying by using of molybdenum oxides was carried out, and the technological process appeared as follows: EAF (30t) → LF (30t) → VD → ESR →Rolling. Results show that throug the new smelting process quality of ingots meets the requirements of H13 die steel, meanwhile, [O], [H] and [N] contents in molten steel reach a low level compared to traditional smelting process. Therefore, it is feasible to smelt H13 die steel by using of molybdenum oxides instead of ferromolybdenum.

Abstract: Friction stir weld fatigue test was performed and the microstructure of the welded joint was analyzed on aluminum 2219-T6. The surface morphology, micro-hardness and grain structure of the welded joint were observed. The fracture surface of the welded joint was observed after the fatigue test. According to the observations, there were more dynamic recrystallizations in the nugget zone and the grain size became smaller in this zone. The grains in the thermo-mechanical affected zone deformed obviously and there were more substructures in the heat affected zone. The hardness values were lower in the thermo-mechanical affected zone and nugget zone. The hardness values distribution shape was W in the upper surface of the joint and probably V in the bottom surface of the joint. The fatigue fractures happened mostly in the nugget zone. There were lots of inner-hole defects in nugget zone on the fracture surface by scan observation. These defects could affect the properties of the welded joint.