Advanced Materials Research Vols. 562-564

Abstract: Pure TiO₂ , Ti _0.75 Fe_0.25 O₂, Ti_0.75 Ni_0.25 O₂, Ti_0.75 Co_0.25 O₂ nanocrystals were prepared by low temperature sol-gel method. The samples were characterized by using transmission electron microscope, X-ray diffractometer and ultraviolet-visible spectrophotometer to study the effect of transition metal ions on the photocatalytic properties of TiO₂ nanocrystals. The results show that the pure TiO₂ and Ti_0.75 Fe_0.25 O₂, Ti_0.75 Ni_0.25 O₂, Ti_0.75 Co_0.25 O₂ nanocrystals were granular and the size of which is 3.5, 2.9, 3.6, 3.9 nm, respectively. The titania anatase phases appear in the pure TiO₂ , the Ti_0.75 Fe_0.25 O₂, Ti_0.75 Ni_0.25 O₂, Ti_0.75 Co_0.25 O₂. The absorption edge of Ti_0.75 Fe_0.25 O₂occur red shift comparing with that of pure TiO₂ and the absorption edge of Ti_0.75 Fe_0.25 O₂and Ti_0.75 Fe_0.25 O₂occur blue shift comparing with that of pure TiO2. The photocatalytic properties of pure TiO₂, Ti_0.75 Fe_0.25 O₂, Ti_0.75 Fe_0.25 O₂, Ti_0.75 Fe_0.25 O₂nanocrystals synthesized at low temperature by sol-gel method were investigated by degrading the methyl orange solution under ultraviolet irradiation. The degradation rate of Ti_0.75 Fe_0.25 O₂is the highest (60%) and that of Ti0.75Co0.25O2 (10%) is the lowest among these catalysts after degradation for 120min.The result shows that the photocatalytic property ofTi_0.75 Fe_0.25 O₂nanocrystals synthesized at low temperature is obviously better than that of pure TiO₂ and Ti_0.75 Fe_0.25 O₂, Ti_0.75 Fe_0.25 O₂.

Abstract: CO2 erosion; Ni-TiN nanocoating; electrodeposition Abstract. Ni-TiN nanocoatings were successfully fabricated by pluse electrodeposition (PED) on the surface of 20 steel. Microstructures of the coatings were investigated by XRD, SEM, and HRTEM. In the CO₂ erosion test, both 20 steel and Ni-TiN nanocoatings were evaluated using the autoclave. The XRD and HRTEM results demonstrated that the Ni-TiN nanocoatings were consisted of Ni phase and TiN phase. And the average diameter of Ni grains and TiN particles were approximately 52 nm and 30 nm, respectively. The CO₂ erosion experimental results indicated that the Ni-TiN nanocoatings showed better corrosion resistance than 20 steel. And CO₂ pressure had great effect on the erosion characteristic of Ni-TiN nanocoatings.

Abstract: Nanocomposite Ni–TiN coatings were prepared by ultrasonic pluse electrodeposition and the effects of ultrasonication on the coatings were studied. X-Ray diffraction analysis was utilized to detect the crystalline and amorphous characteristics of the composite coatings. The surface morphology and metallurgical structure were observed by scanning electron microscopy, high-resolution transmission electron microscopy and scanning probe microscopy. The results show that ultrasonication has great effects on TiN nanoparticles in composite coatings. Moreover, the introduction of ultrasonication and TiN particles led to the formation of smaller nickel grains. The average grain diameter of TiN particles was 33 nm, while Ni grains measured approximately 53 nm.

Abstract: Recently, MHD is a high-efficiency and non-pollution technology. In Xiangtan University a power generation experimental set-up using the ferriferous oxide magnetic fluid in which we use the electrometer instead of external load to directly measure the electromotive force of the test magnetic fluid in the tube is established to investigate the relationship of the variables of the test fluid and the performance of the power generation. Based on the setup proposed by Hiroshi Yamaguchi in Japan, we create an experimental set-up using a new idea. Furthermore, the electromotive force and internal resistance which the magnetic fluid in the tube generates decrease with the temperature, and the electromotive force increases with the velocity of the magnetic fluid, in other words, it increases with the Reynolds number, which is in good agree with the theoretical analysis. We have also showed the image of the electromotive force, velocity and the temperature, which has helped to develop the power generation.

Abstract: Electrospinning is a simple and practical method for fabricating uniform fibers with diameters range from several micrometers down to a few nanometers. In order to achieve highly ordered arrays of nanofibers, a novel and feasible approach, named contact-transfer printing of electrospun fibers, is reported in this paper. Via this method, large-scale aligned nanofibers on various rigid or flexible substrates can be assembled. This technique is demonstrated to be efficient on transferring of electrospun nanofibers with a high degree of alignment (~88.2%) on a SiO2 substrate. In addition, it is found that the printing outcome highly depends on the pressure between collecting and receiving substrate.

Abstract: This paper focuses on a typical automotive piston material to characterize its fractographic appearance after low cyclic fatigue test. The fatigue fracture of this heavily alloyed Al-Si alloy takes place in a brittle manner. The crack nucleated from a large intermetallic colony close to the specimen surface. When the crack encountered the intermetallics, it might progress along the interface among the intermetallics or the interface between the intermetallics and the eutectic. The debonded Al-Si eutectic region and intermetallics provided a weak material path for the crack propagation. A fatigue fracture mechanism in the heavily alloyed Al-Si alloy is elucidated.

Abstract: Power spinning is one of the effective ways to refine grains of material and improve its mechanical properties. To explore the severe plastic deformation mechanism of power spinning for polycrystalline metal, the construction of mesoscopic plastic constitutive model and geometrical model was introduced in detail. A 3D representative volume element (RVE) of microstructure for polycrystalline materials was developed based on the finite element software ABAQUS by Matlab and Python script, and the parametric finite element gridding was realized with the LaGriT tool, which lays a solid foundation for the finite element simulation and prediction of microstructure evolution for power spinning of polycrystalline metal.

Abstract: In the Nb–Si–N films, Si content (CSi) was varied in each series by changing the power applied on the Si target, whereas the power on the Nb target was kept constant. The microstructure of the coatings was examined by XRD and in cross-section by transmission electron microscopy (TEM). Depending on TS and pN2, the deposition rate showed significant variations from 0.04 to 0.18 nm/s. The correlation between film morphology (preferential orientation of crystallites, grain size, column dimensions, thickness of the SiNx layer covering NbN crystallites) and the deposition conditions (power applied on Si target, temperature, nitrogen partial pressure and deposition rate) provides useful information for optimizing the deposition process.

Abstract: In order to investigate the process of ISF through numerical and experimental approaches, finite element method (FEM) models for two truncated pyramids were developed to simulate the process and the simulated thickness distributions were compared with experimental results. The influences of process parameters on equivalent plastic strain, the maximum equivalent plastic stress and forming force were also discussed. The results show that ISF process is basically to be a plane strain deformation. Wall angle is a more significant influence factor of forming performance than tool diameter and depth increment. With increasing tool diameter, decreasing wall angle and step increment, uniform thickness distribution will be achieved. However, more wall angel, less tool diameter and depth increment contributes to decrease forming force. Additionally, process parameters have no connection with work hardening for a certain material during ISF.

Abstract: To improve photocatalytic activity of hematite, the electronic structures of F, and N doped hematite were studied via the first-principles band calculations with GGA+U methods. By analyzing the band structures of pure and doped hematite, we showed that the significant acceptor levels were induced by N dopants, whereas F dopants created shallow donor levels and Fermi energy entered the conduction bands. Our findings proposed that p-type dopant N was in favor of realizing the expectation of producing hydrogen in the visible-light photoelectrochemical (PEC) water splitting without voltage bias, and n-type dopant F was helpful to solve the problem of recombination of photo-produced electron-hole pairs The results of our calculation should be applicable to the improvement of photocatalytic performances of hematite.