Advanced Materials Research Vols. 79-82

Abstract: Silver palmitate was prepared by chemical deposition method using palmitate acid, sodium hydroxide and silver nitrate as raw materials in water system. The structure and thermal properties of silver palmitate were characterized by SEM, XRD, FTIR, TG and DSC. The results show that silver palmitate has a good purity and well-defined layer structure with triclinic phase. TG and DSC curves demonstrate that silver palmitate decomposed at 230 and 250oC. One of the decomposed products at 230oC is a free acid with melting point at 52oC. The endothermic peak at 120oC attributes to the order-disorder phase transition. The three endothermic peaks at 159, 166 and 175oC assign to reversible phase transitions among intermediate phases.

Abstract: A novel precision casting technique for TiAl based alloy was described in this work, called the permanent mold suction casting technology，and the blades of Ti-47Al-2Si、Ti-47Al-2W-0.5Si、Ti-47Al-2W-0.5Si -0.5B were get by this technology. The structures of these blades were studied. The results of this study indicate that microstructure is sensitive to heat treatment and composition. The average grain size is 30 um before heat treatment. The grain size of TiAl based alloy is grossed by heat treatment at 1573 for 5h and furnace cooling, especially Ti-47Al-2Si. The addition of boron, the grain size of Ti-47Al-2W-0.5Si-0.5B is smaller than Ti-47Al-2W-0.5Si. The γ-TiAl based alloys have equiaxed grain in cross section, but the surface microstructure of γ-TiAl based alloys have more fine equiaxed grain than inside due to high cooling rate of mold.

Abstract: Microstructure evolution of peritectic Al-25at.%Ni alloy during directional solidification with pulling velocity ranging from 2 to 500m/s is investigated. The directional solidified alloy is composed of Al3Ni2, Al3Ni phase and eutectic (Al3Ni+Al) phase. When pulling velocity ranges from 2 to 5m/s, Al3Ni phase grows into an integral matrix. Majority of primary Al3Ni2 is consumed by peritecti reaction and transformation behind the peritectic interface with pulling velocity ranging from 2 to 20 m/s. While pulling rate increases, major Al3Ni phase direct solidifies from liquid. With cooling rate increasing, Al3Ni2 phase content firstly decreases and then increases, while the Al3Ni phase content decreases throughout.

Abstract: In the article this is a new way to prepare Ti-6Al-4V alloy rod and blade by metal mold vacuum suction casting. The effects of hydrogen on the suction casting is also studied. It is found that the alloy melt can be sucked up easily by the mold and has a better fluidity because of H2. Hydrogen can make the electrical current for suction casting decrease sharply compared with the electrical current in Ar. Hydrogen can refine the grain size of the alloy rod and blade. Compared with the unhydrogenated specimen, the peak stress of the hydrogenated specimens increase about 20%, because hydrogen decreases the volume fraction and size of shrinkage porosity.

Abstract: SOL (stand-off layer) damping treatment is the most effective method to improve the damping characteristics of the base structure compared with unconstrained and constrained layer damping treatment. In this case, the viscoelastic layer is sandwiched between the SOL and the constraining layer. During vibration, the SOL acts as a strain magnifier which magnifies the shear strain in the viscoelastic layer by increasing the distance between the viscoelastic layer and the neutral axis of the base structure thus dissipates more vibration energy. The equations of motion root in kinematic equations, constitutive equations and equilibrium equations of force and moment, and constitute one variable (lateral deflection) with order differential equation and two variables (axial deflections of the base beam and the constraining layer) with order differential equation of motion. Together with the boundary conditions, the transfer function method and the finite element method are adopted to analyze the damping characteristics of the composite structure. In distributed function method, the equations are transferred to state space form. In finite element method, the lateral deflection is interpolated by Hermite interpolation function and the axial deflections of the base layer and the constraining layer are interpolated by Lagrange interpolation function. At last, the predictions of the two analytical methods are validated against the commercial software ANSYS. Close agreements are found among the three methods. To achieve the expected effect, the SOL must have high shear stiffness and low bending stiffness so it does not significantly influence the flexural rigidity of the base structure but does not absorb the shear stress desired to be passed on to the viscoelastic layer. This paper is focus the application of SOL damping treatment on cantilever beam model, but it is essential to note that the model can be extended to complex structures such as plates and shells. We can select the slotted SOL damping treatment which could effectively avoid the increase in bending stiffness but also maintain high shear stiffness as the substitute.

Abstract: The anti-static and anti-radiation properties of functional fabrics containing stainless steel microfilament were investigated in this paper. Three specifications of stainless steel microfilaments( diameter: 0.035mm、0.040mm and 0.050mm ) and cotton yarn were twist into composite yarns. The functional fabrics were woven by cotton yarn as warp, both cotton and the composite yarn as weft. The fabric performances were tested after woven and some treatments, especially the anti-static and anti-radiation properties. The results showed that with stainless steel microfilament increases in fabric, the amount of electrostatic charge on fabric becomes smaller. The results also showed that these fabrics had a good anti-radiation ability. So these functional fabrics have good application prospects in protective clothing and technical textiles.

Abstract: Carbon nanotubes (CNTs)/hydroxyapatite (HA) nanocomposites have been successfully fabricated by a novel method for the biomedical applications, which is in situ growing CNTs in HA matrix in a chemical vapor deposition (CVD) system. The results show that it is feasible to in situ grow CNTs in HA matrix by CVD for the fabrication of CNTs/HA nanocomposites. Multi-walled CNTs with 50-80 nm in diameter have been grown in situ from HA matrix with the pretreatment of sintering at 1473K in air. The nanocomposites are composed with carbon crystals in CNTs form, HA crystallites and calcium phosphate crystallites, one of most important CaP bioceramics. And the CNTs content is about 1% proportion by weight among the composites in our experiments, which can enhance the HA mechanical properties and the CNTs content does not affect the HA performances. These CNTs/HA nanocomposites have the potential application in the biomedical fields.

Abstract: The morphological differences of chitosan (CS) in the hydroxyapatite (HA)/CS nanocomposites were investigated in detailed, which were prepared via in situ hydrothermal precipitation. The results show that the obtained nanocomposites have excellent crystallinity and the crystal has excellent ordered structure, which is important to the composites performances in the biomedical application. Moreover, the CS arrangement and crystallinity in the composites greatly depend on the hydrothermal temperature and the pH value of precipitating agent. The temperature ranging from 373 to 413K and pH value of precipitating agent ranging from 12 to 14 were favorable to the crystallization and oriented growth of CS molecules in the composites. The CS crystals with better arrangement are assembled in the order of layer-by-layer in these composites.

Abstract: In this paper, setting 1.06 μm Gaussian modulated pulse electromagnetic wave as irradiation sources, the influences of structural parameters on reflectivity are analyzed by finite different time domain (FDTD) method. The results show that the filled factor and height are key factors for circular tube relief structure with non absorption. The optimal height could be set to 0.2 μm, which is one odd time of the ratio of incident wavelength λ and four equivalent refractive index 4N, then the best filled factor is between 0.7 and 0.9, the ratio of inner and outer diameter could be set between 0.4 and 0.6, and the structure period has little significant influence. Compared with cylinder solid structure, it has been discovered that circular tube hollow structure could weaken the backward energy of electromagnetic wave, and it would be more suitable for antireflection structure than solid cylinder structure. Moreover, we design two another circular tube relief structures simulations with different extinction coefficients, it is found that the reflectivities are lower up to 0.00016% than the non absorption one.

Abstract: This work presents the results obtained in the development of phosphotungstic acid/semi-coke catalysts in the oxidative desulfurization (ODS) process of diesel oil using hydrogen peroxide as the oxidizing agent. Phosphotungstic acid /semi-coke (60wt%) prepared by impregnation. These catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), The effect of the amount of catalyst used , on the efficiency of desulfurization was investigated. In addtion. the diesel after oxidation and extraction was analyzed by GC-FPD for sulfur content. The chromatograph shows that virtually all the sulfur containing compounds in diesel were removed.