Advanced Materials Research Vols. 1033-1034

Abstract: The effects of milling variables on the particle sizes and purity of mechanically alloyed Nb-30W powders were quantitatively investigated using orthogonal test of three factors consisting of milling time A (12h, 24h and 48h), ball-to-powder ratio B (6:1, 10:1 and 20:1) and solid-to-liquid ratio C (1:0.2, 1:0.5 and 1:1) at three levels in order to optimize the milling variables of mechanically alloyed Nb-30W powders. Results indicated that the particle size was mainly determined by the solid-to-liquid ratio and the purity of powder was mainly affected by the ball-to-powder ratio and the milling time; best combination of all variables was found to be A2B2C1 with the particle size 12.62μm and Fe content 0.399%. After hot pressed, A2B2C1 combination obtained the highest mechanical properties. With the refining of particles during milling, the Fe contaminations of milled powder increased and were dissolved into Nb lattices to form Nb (Fe) solid solution; meanwhile, macro stress caused by plastic deformation of Nb particles was released.

Abstract: Using the first principles calculation method calculated the Mg substitutional atoms occupying law in LaNi₃ alloy. The results of total energy showed ,when Mg atoms occupy the bit of 6c,LaNi₃ alloy is more stable. And substitutional atoms tend to non adjacent. The result of size effect and electronic structure showed that ,the size effect is a major determinant of substitutional Mg substitutional atoms.

Abstract: The novelty of this paper is the use of a meshless local collocation method based on the multiquadric radial basis functions for free vibration analysis of functionally graded plates. This method approximates the governing equations based on first-order shear deformation theory using the nodes in the support domain of any data center. The natural frequencies computed by the present method are in good agreement with the element-free solutions of Zhao et al.

Abstract: A nth-order shear deformation theory for free vibration of the isotropic plates resting on a two-parameter Pasternak foundations is developed. The present theory does not require shear correction factor, and satisfies the zero transverse shear stress boundary conditions on the top and bottom surface of the plate. Governing equations are derived from the principle of virtual displacements. Meshless global collocation method based on the thin plate spline radial basis function is used to solve the governing differential equations. The accuracy of the present theory is demonstrated by comparing the present results with available published results.

Abstract: The ablation behaviors of 3D fine woven pierced carbon/carbon (C/C) composites were tested on an arc heater and their ablation morphologies were observed by scanning electron microscopy (SEM). It shows that ablation of 3D fine woven pierced C/C composites tends to start at interfaces, defects and pores. Cracks mainly yield at the boundaries of carbon fiber bundles, interfaces of carbon fiber felts during the ablating processes. The ablation properties of 3D C/C composites in parallel direction are better than that in vertical direction. In addition, the work indicates that the ablation process is mainly controlled by mechanical denudation.

Abstract: Polypropylene (PP)/ethylene-vinyl acetate (EVA) blends were prepared using a twin-screw extruder by melt blending method. The influences of the EVA contents in PP/EVA blends on crystallization behavior and mechanical properties were investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). XRD results show that the EVA not change the crystal structure in the blends but only decrease the intensity of the diffraction peak. DSC results showed that the melting point and crystallization point decreased when EVA added to the blend. The tensile properties of PP/EVA blend become much better.

Abstract: The effect of graphite content on formation of decarbonization layer and corrosion resistance of zirconia graphite materials were studied by the corrosion test in induction furnace, and the effect of decarbonization layer on corrosion of zirconia graphite materials was also analysed by the kinetic models for the corrosion of SEN in mold, the result show that Thickness of decarbonization layer of slag line is decreasing with the increase of graphite content. Corrosion of zirconia graphite materials in steel liquid / slag interface is characterized by the features of consecutive reaction:original layer→decarbonization layer→corrosion layer, and k₁, and k₂ are their reaction rate constant respectively.when we adjust graphite content, k₁ and k₂ will be change in opposite directions, so graphite content with well corrosion resistance depend on the condition of continuous casting

Abstract: High-strength concrete in the autoclaved-curing was made by the way of mixing single and double doped. The compressive strength of concrete and the morphology of hydrates in concrete containing ground granulated blast-furnace slag (SG) and Quartz sand (QS) have been investigated using XRD and SEM measurements. The results show that quartz sand also possesses effective pozzolanic property in the steam-autoclaved stage. The mixed proportion of QP:SG=1:1 is the best when the dose is 30%.The paste became denser through double mixing. When the doses is 10-35%, SG for the improvement of concrete compressive strength is higher than the quartz sand.

Abstract: A novel celsian/yttrium silicate coating was deposited on carbon fiber reinforced silicon carbide matrix (C/SiC) composite, using BaO-Al₂O₃-SiO₂ (BAS) glass andY₂O₃ powder as starting materials. The effects of sintering temperatures on microstructure and performance of coatings were studied. The results show that the final phases of sintered coatings are composed of celsian, yttrium silicate and remnant glass. The coating are dense, crack-free and pore-free in macroscopic scales when sintered at temperatures above 1400°C. The crystal grains in the coating grow too large, and the coating is loose in microstructure when sintered at temperatures higher than 1450°C. The coated samples sintered at 1450°C for 30min, which have the densest morphology and microstructure, have the lowest weight loss of 0.13 % after oxidation at 1500°C for 90 min.

Abstract: Foamed concrete is prepared by the use of volcanic rock powder and ordinary portland cement and by means of chemical foaming method. The chemical composition and morphology of volcanic rock powder are analyzed,and the effect of volcanic rock powder addition into the portland cement slurry on the properties of foamed concrete is discussed.The results that the properties of the foam concrete could be prepared by controlling the addition of the volcanic rock powder content is 20%, The Compressive strength is as high as 1.36Mpa. The thermal conductivity is 0.048W/(m·K) and the dry density is 254kg/m³ for 28 days curing age. The main compositions of volcanic rock powder is SiO₂ and the volcanic rock has a large number of closed and open pores.