Advanced Materials Research Vol. 700

Abstract: Metallurgical-grade silicon is purified by using electron beam melting (EBM) technology in this paper. The distribution of impurity aluminum in silicon is uneven in ingot preparation, which shows the enrichment trend that from the bottom to the top and from the edge to the centre of the ingot. The content of aluminum is low in marginally place of ingot, and is lower than the detection limit of ICP-AES (1×10^-5%). The theoretical analysis on aluminum evaporation is conducted. The relation between volatilization of impurity aluminum and surface temperature of melting silicon and melting time is introduced from Langmuirs equation and Henry law, which indicates that the removal rate of aluminum increase with the rising of the temperature in melt surface and the expanding of the time, the experimental results are in accord with the calculated one.

Abstract: This paper explains the advantages and shortcomings of waterborne marking paint, based on technical characteristics thereof, describes the physical and chemical properties of said paint required in China, discusses the application status of said paint in China and abroad, and proposes the application trend of said paint in China. The results showed that: the waterborne marking paint has little damages on human and environment because of less volatile organic content (VOC), and has many other advantages such as good retroreflective performance, more conveniently cleaning effect for applying equipment and good skid resistance, etc., while it has the shortcomings of thermal sensitivity, easily freezing performance and metal corrosion, for example; the waterborne marking paint has been used with the third amount based on the total of road marking paint in China, but a further progress needs to be made for the waterborne marking paint in technology, application and market promotion in order to improve its field of application.

Abstract: The mechanical behaviours of SiCp_A356 composite at room and elevated temperature were investigated. The yield strength, the tension limit and Young’s modulus drop obviously with the rising temperature. The hardening cycle occurs during 20°C~150°C, but weakens with rising temperature. The softening cycle appears between 200°C~300°C, but increases with rising temperature. The relaxation performance is similar to that of a normal metal material. The creep constitutive model was presented and finally the micro fracture mechanics was analyzed.

Abstract: The total stress consists of the symmetrical stress and asymmetrical stress, and the latter is connected to the couple stresses. A linear constitutive relation is established between the couple stresses and curvature tensor, three material parameters including the rotational modulus are involved in the generalized linear elasticity. A numerical analysis with the finite element method has been accomplished on the scale effect of copper in simple plane shearing. It is shown that a sharp drop of the stress symmetry occurs when the copper structure scale varies from some 1mm to 0.1mm in the example. When we analyze the physical and mechanical properties of cooper structure under micro size scales, the generalized linear elasticity should be used, and the asymmetrical feature of stress tensor must be considered.

Abstract: Some oil wells have adverse working environments, material selection and sizes optimization of casing material for gas-lift well under existence of CO₂ corrosion are very important. This paper presents the development background, sizes optimization of casing material for gas-lift well, effect of CO₂ on material of casing, casing material selection. By testing, the study above has a strong practicality and can be suitable for the well condition of on-the-spot application.

Abstract: A new material of cation platinum (II) complex has been synthesized and characterized. The new material binding properties with human telomeric G-quadruplex DNA (G₄-Htel DNA) and ct-DNA were examined by UV-Vis and CD spectroscopic methods. The results showed that complex exhibited higher binding affinity and binding intensity to G₄-Htel DNA (up to K_b = 1.54×10⁶ M^-1) and with selectivity (up to 11-fold) over duplex DNA. The CD results suggests the antiparallel structure of G-quadruplex can remain stable in the presence of platinum complex and the complex may bind to DNA by intercalation mode.

Abstract: A novel porous TiO₂-Al₂O₃ composite as a kind of environmental material was prepared by sol-gel method. The pore size distribution is not even in the whole pore size range. When pore size is 7.049 nm, the maximum pore volume of the material is 0.06627 cm³·g^-1. The average pore size for the material is 14.56 nm and the total pore volume is 0.3945 cm³·g^-1, as calculated from BJH method. Photocatalytic degradation of methyl orange can be regarded as following first order kinetic reaction. After 90 min of reaction, methyl orange degradation on the material was 77.0% and the total dye decoloration rate was 95.1%, containing both adsorption and photocatalytic degradation. The intensities of both peaks in visible and UV regions decreased sharply during photocatalytic degradation process.

Abstract: Ce, Nd and Gd doped strontium titanate nanomaterial was prepared by a sol-gel method. Effects of transition metals doping on photocatalytic activities of the prepared materials were studied. The pure strontium titanate had photocatalytic degradation activity of 31.0%. The maximum degradation rate happened at Ce content of 20% and nearly 32.5% of the initial methyl orange was degraded on the material after 30 min of irradiation. Although there was a slight variation of photocatalytic degradation rate with the increasing Nd doping content, the materials doped with Nd had lower photocatalytic activity compared with pure strontium titanate. Nearly all the samples doped with Gd in the range up to 30% had much lower activity that the pure strontium titanate.

Abstract: Ce_1-xDy_xFe_1.9(x = 0, 0.02, 0.05, 0.1) alloys were prepared successfully by means of arc-melting and the following homogenization. XRD patterns show all alloys are indexed as MgCu₂-type C15 cubic Laves phase structure. With the Dy substitution of Ce, the Curie temperatures from ferro-to para-magnetism become gradually enlarged. The values of for a magnetic-field change from 0-5 T at 234, 246, 268, 303 K are 31.7, 26.4, 21.8, and 17.2 J kg^-1 K^-1 for x = 0, 0.02, 0.05, and 1, respectively.

Abstract: We have performed the first-principles calculations onto the structural and electronic properties of GaN nanoribbons with zigzag edge (ZGaNNRs). The results show that, the lowest unoccupied conduction band (LUCB) and the highest occupied valence band (HOVB) are always separated, representing a semiconductor character for the ZGaNNRs. In addition, the majority and minority spin bands are fully superposition and therefore the ZGaNNRs are non-magnetic. As the nanoribbons width increase, band gaps of ZGaNNRs decrease monotonically and become close to their asymptotic limit of a single layer of GaN sheet. It is found that the fewer coordination number will lead the most electrons to range in higher energy region of the occupancy state.