Advanced Materials Research Vols. 295-297

Abstract: Zr_45.1Cu_42.3Al_8.7Si_1.4Y_2.5 (at. %) metallic glass alloy was prepared by using copper mould casting. The crystallization behaviors of the alloy during continuous heating are investigated mainly by differential canning calorimeter (DSC). The activation energies were obtained from the Kissinger and Doyle equations. The results show that the activation energies of glass transition (E_g), crystallization (E_x) and peak crystallization (E_p) are 365kJ/mol, 281 kJ/mol and 279 kJ/mol, respectively. The crystallization activation energies are all less than the corresponding data of ZrCuAlSi alloy, the results show that thermal stability was decreased with the Y addition.

Abstract: The effect of limestone powder on immobilization of chlorine ion of Portland cement was studied by the method of the chemical analysis. The immobilization of chlorine ion of Portland cement, which was hardened by cement clinker or cement clinker and gypsum mixed limestone powder with different proportions, was tested at 28d. The results show that the amount of immobilization of chlorine ion of Portland cement increases more than doubled, and the free chlorine ion content decreases 41% without gypsum, when the limestone powder content increases from 0% to 12%; the immobilization content of chlorine ion increases first, and then decreases, the free chlorine ion content decreases a little with gypsum, when the limestone powder content increases from 0% to 8% .

Abstract: Based on CSP technics, using Gleeble1500-D hot simulation machine, making the single, dual, multi-pass compression experiment of Q345B steel with rare earth Nd respectively, different deformation conditions influencing Q345B steel of recrystallization behavior and the microstructure evolution rule in the hot rolling process have been studied. The results show that: the single, dual-pass experiments of Q345B steel with rare earth Nd are according with general experimental rules. According to single, dual-pass results, we establish multi-pass compression project. In that project, the grain samples with rare earth element Nd are finer than others. It explains that appending rare earth Nd has the obvious function of refining grains. At the same time, the degree of refining grains is different in the different project. It explains that in order to obtain fine grains, we should choose feat technics. By contrast, we can educe that the grains are more fine and uniform in a project.

Abstract: According to requirements of online steel ball surface defect inspection, the automatic detection method of spherical surface defect on the track has been posed. To ensure photographing of the whole steel ball surface, the six CCD video cameras are used in this system. To overcome steel ball surface reflection, the red LED light source is used, and then the real and clear images are got. The steel ball surface defect is recognized accurately by means of image recognition technology and image reconstruction technology etc. This method provides theoretical basis and technical support for ball defection and quality classification.

Abstract: Titanium dioxide nanotube array films on aluminum plate were prepared via liquid phase deposition (LPD) method. The samples were characterized by field-emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR). The results show that the nanotube array films’ morphology depends on the anodic aluminum oxide (AAO) structure and deposition time. The titanium dioxide nanotube’s outside diameter is about 250 nm, the wall thickness is approximately 40 nm. The as-prepared TiO₂ array films are amorphous and anatase appeared after calcining at 400°C for 2 hrs. FT-IR spectrum indicates that there are lots of hydroxyl groups on the surface of AAO. When AAO was immersed into 0.1 M (NH₄)₂TiF₆ solution at room temperature, AAO was dissolved in the solution and the holes became wide. The hydrolysis reaction was shifted to the right-hand side, TiO₂ particles locked in-situ on the inner surface of the anodic alumina pore induced by hydroxyl group, thus nanotube array film was obtained.

Abstract: Swirling flow in an immersion nozzle is effective on improving quality of casting block and casting speed in continuous casting process of steel. However, a refractory swirl blade installed in the nozzle is liable to cause clogging, which limit the application of the process. In this study a new process is proposed, that is a rotating electromagnetic field is set up around an immersion nozzle to induce a swirling flow in it by Lorentz force. New types of swirling flow electromagnetic generator are proposed and the effects of the structure of the generator, the coil current intensity and frequency on the magnetic field and on the flow field in the immersion nozzle are numerically analyzed.

Abstract: Highly polarized light transmission from GaN based light emitting diode is proposed using a double-layer metallic grating film and a dielectric transition layer. TM mode transmission and the polarized extinction ratio (ER) are calculated using commercial software, based on a full vector implementation of Rigorous Coupled Wave Analysis (RCWA) algorithm. Such a thin-film double-layer grating with subwavelength metallic stripes are designed and simulated by perfect parameters of period, thickness and filling factor for achieving good polarization properties. It is found that TM transmission and ER are almost stable and flat under different slit arrays of the double-layer grating. The polarized structure shows larger width of incident wavelength with a transition layer of a low refractive index than that of a high refractive index, but higher TM transmission and ER can be obtained for low refractive index transition layer. Flat sensitivity and high transmission of the TM mode on the double-layer metal grating thickness have been achieved. Up to 100nm range of the grating height can be employed to achieve TM transmission more than 92% while ER > 20dB. The results provide guidance in designing, optimizing and fabricating the integrated GaN-based and polarized photonic devices.

Abstract: The influence of thermomechanical parameters on the microstructure and retained austenite characteristics in a hot rolled Al-Si-Mn transformation induced plasticity (TRIP) steel based on dynamic transformation of undercooled austenite was investigated, in an effort to produce a desired microstructure and better control retained content. The results show that strain rate had a minor effect on the microstructure, but the volume fraction of retained austenite decreased with increasing strain rate. Decreasing coiling temperature caused a decrease in volume fraction of retained austenite and decrease in the size of bainitic ferrite platelets. Increasing the isothermal holding time during bainite treatment, the volume fraction of retained austenite first gradually increased then decreased. Moreover, The deformation of undercooled austenite not only can influenc the transformation of bainite, but also can refine the grain size of bainite, increase the chemical and mechanical stabilization of retained austenite.

Abstract: The spark plasma sintering (SPS) technique was employed to investigate the fabrication of cerium-doped lutetium orthosilicate (Ce:Lu₂SiO₅, LSO) polycrystalline scintillation ceramics starting from nanosized Ce:LSO powders synthesized by sol-gel processing. Fully-densed polycrystalline Ce:LSO ceramics with fine grains were fabricated on optimal sintering conditions of 1350°C for 5 min under pressure of 50 MPa. Translucent monolithic Ce:LSO ceramic sample was obtained with excellent luminescent characteristics after being annealed in air at 1000°C for 15 hrs. Under 360 nm UV excitation, a broad emission peak centered at 425 nm was detected for Ce:LSO ceramic, with a short decay time of only 9.67 ns. The luminescence intensity of annealed sample(doped by 0.5mol% Ce³⁺) is 3 times greater than that of BGO crystal under X-ray excitation. The good luminescent characteristics make Ce:LSO polycrystalline ceramics a promising scintillator candidate with high performance for radiation detection in future.

Abstract: We employ density functional theory to investigate TiAl₃/Al interfaces with the orientation of (001) [100]_Al//(001)[100]_TiAl3 by electronic structures, relaxed atomic geometries and adhesions. The preferable interfacial atomic structure is that wherein Al atoms continue on the natural stacking sequence of bulk TiAl₃. Two types of TiAl₃ (001) slabs, Ti-centered, all Al atoms, are adopted to compare interfacial energy, interfacial electronic structure. The calculated adhesion energies W_ad of the two types of interface are very close, and are quantitatively in agreement with other calculated results of Al on the carbide and nitride, but much lower than the (111)_Al[1 0]_Al//(0001)_TiB2[11 0]_TiB2 adhesion energy. We have thoroughly characterized the electronic structure and determined that the metallic Al-3p and Ti-3d bonding constitute the primary interfacial bonding interaction.