Advanced Materials Research Vols. 306-307

Abstract: The transmission properties of Thue-Morse quasi-periodic one-dimensional photonic crystals (1DPCs) containing superconducting material are theoretically investigated based on the transfer matrix method. It is shown that the 1DPCs can possess a same photonic band gap property as the periodic structure superconducting PC. The results of transmittance spectra show that the cutoff frequency can be manipulated through the thicknesses of the superconductor and dielectric layers as well as the ambient temperature of the system. It is observed that the shift of cutoff frequency becomes more noticeable by adjusting the thickness of the superconductor layer than that of the dielectric one. Furthermore, the cutoff frequency becomes very sensitive when the system temperature is tuned to close vicinity of the critical temperature of the superconductor.

Abstract: A sensitive immunoassay based on immunomagnetic beads for measuring carcinoembryonic antigen (CEA) concentration in cancer cells was presented in this article. We used immunomagnetic beads to separate CEA in the gastric cancer cells and those CEA could be marked with horseradish peroxidase (HRP) labeled anti-CEA secondary antibody. The HRP could catalyze non-fluorescent 10-acetyl-3,7-dihydroxyphenoxazine (ADHP) with hydrogen peroxide (H₂O₂) to fluorescent products. Therefore, the CEA concenctration was quanlified by flourescence intensity at 585 nm emission wavelength. The flourescence intensity of the product responged well linearly to CEA concentration in the range from 3.0 to 60 ng/mL with a lower detection limit of 1.5 ng/mL(3σ). This method could be applied to determine tumor markers in gastric cancer cells.

Abstract: The dynamics of a two-dimensional vortex system in superconductors with periodic artificial columnar pinning is studied. The ground state at field B = 3B_f can be either anisotropic or isotropic, dependent on pinning strength and size, here B_f is the matching field where the number of vortices equals that of pins. The transport curves are dependent on the ground vortex structures and anisotropic ground structure may result in anisotropic velocity-force curve. Results indicate that the ground structure can be detected from the transport property. We also discover that a jump in velocity-force curve accompanies a structure transition.

Abstract: Nano-hexaferrite SrFe₁₂O₁₉ has been prepared using the aqueous solution method. The structure and magnetic properties of SrFe₁₂O₁₉ have systematically been investigated by X-ray diffraction (XRD), Thermo gravimetric (TG), Fourier transform infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM), as well as Vibrating Sample Magnetometer (VSM). The XRD and TEM results showed that the samples are composed of SrFe₁₂O₁₉ nano-particles which are on average 70×50nm in dimensions when treated at 1200°C for 2 hours. The magnetic properties indicated that the saturation magnetization and the intrinsic coercivity were 48 Am²/kg and 506KA/m, respectively. The aqueous solution method is generally applicable to produce the nano-hexaferrite SrFe₁₂O₁₉ and is proved to be a promising method for fast synthesis of nanometer materials using nitrate.

Abstract: Core/shell type nanoparticles with an average diameter of 20nm were synthesized by chemical precipitation method. Firstly, Monodisperse Fe₃O₄ nanoparticles were synthesized by solvethermal method. FeSO₄ž7H₂O and NaBH₄ were respectively dissolved in distilled water, then moderated Fe₃O₄ particles and surfactant(PVP) were ultrasonic dispersed into the FeSO₄ž7H₂O solution. The resulting solution was stirred 2 h at room temperature. Fe could be deposited on the surface of monodispersed Fe₃O4 nanoparticles to form core-shell particles. The particles were characterized by using various experimental techniques, such as transmission electron microscopy (TEM), X-ray diffraction (XRD), AGM and DTA. The results suggest that the saturation magnetization of the nanocomposites is 100 emu/g. The composition of the samples show monodisperse and the sides of the core/shell nanoparticles are 20-30nm. It is noted that the formation of Fe₃O₄/Fe nanocomposites magnetite nanoparticles possess superparamagnetic property.

Abstract: Triclinic and hexagonal structure of TbBO₃ was synthesized by Sol-Gel combustion method and high temperature solid state method respectively. The TbBO₃ crystal was grown by fluxing Czochralski(CZ) method and LiBO₂ as flux. The crystal structure was studied by FT-IR and DTA. The results of powder magnetic susceptibility of hexagonal one showed that TbBO₃ may be a good candidate magneto optical material.

Abstract: Fe-28Al and Fe-28Al-10Ti alloys were prepared by mechanical alloying and hot pressing. The phases and dry sliding wear behavior were studied. The results show that Fe-28Al bulk materials are mainly characterized by the low ordered B2 Fe₃Al structure with some dispersed Al₂O₃ particles. Fe-28Al-10Ti exhibits more excellent wear resistance than Fe-28Al, especially after long distance sliding wear test. There are obvious differences in wear mechanisms of Fe-28Al and Fe-28Al-10Ti alloys under different testing conditions. Under the load of 100N, there is plastic deformation on the worn surface of Fe-28Al. The main wear performance of Fe-28Al-10Ti is particle abrasion, the characteristics of which are micro cutting and micro furrows, but micro-crack and layer splitting begin to form on the surface of Fe-28Al. Under the load of 200N, serious plastic deformation and work-hardening lead to rapid crack propagation and eventually the fatigue fracture of Fe-28Al. Plastic deformation is the main wear mechanism of Fe-28Al-10Ti under the load of 200N, which are characterized by micro-crack and small splitting from the worn surface.

Abstract: Experiments were conducted to fabricate the Al₄C3 particles by powder in-situ synthesis process under argon atmosphere and examine the grain refinement of AZ91D magnesium alloy with the addition of 0.6%Al₄C₃(hereafter in mass fraction,%). By means of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS), the results show the successful fabrication of Al₄C₃ particles. After adding 0.6%Al₄C₃, the average grain size of AZ91D magnesium alloy decreased from 360μm to 243μm. Based on the differential thermal analysis (DTA) results and calculations of the planar disregistry between Al₄C3 and α-Mg, Al₄C3 particles located in the central regions of magnesium grains can act as the heterogeneous nucleus of primary α-Mg phase.

Abstract: Dislocation configurations in two single-crystal superalloys during high-temperature low-stress creep (1100°C, 137 MP) were illustrated schematically with the use of transmission electron microscope (TEM). For an alloy with a small lattice misfit, the dislocations move in the combination of climbing and gliding processes. In the primary stage, the dislocations first move by slip in the g-matrix channels. When they reach the g¢ cuboids, they move by climb along the g¢ cuboid surfaces. In the secondary creep stage, dislocation reorientation in the (001) interfacial planes happens slowly, deviating from the deposition orientation of <110> to the misfit orientation of <100>. For an alloy with a large lattice misfit, the dislocations are able to move smoothly by cross slip in the horizontal g channels. The dislocation reorientation from the deposition orientation of <110> to the misfit orientation of <100> in the (001) interfacial planes can be completed in the primary creep stage.

Abstract: Based on the empirical electron theory of solids and molecules theory(EET), the valence electron structures(VESs) of the strengthening phases Al₃Fe and Al₆Fe in Al-Fe alloy are calculated, then the stability of Al₃Fe and Al₆Fe, the precipitated sequence under the non-equilibrium solidification, the phase transition during aging and the effects of alloy elements are discussed. The results show that the values of covalent electron pairs on the strongest bond n₁, the total forming bond ability F, and the number of atom state group σ_N of Al₃Fe and Al₆Fe are bigger than that of Mg₁₇Al12 and Mg₂Si, so the stability of Al₃Fe and Al₆Fe is better. The total forming bond ability of Al₆Fe is far smaller than that of Al₃Fe, so Al₆Fe generates first under the equilibrium solidification. The strongest bond of Al₆Fe is weaker than that of Al₃Fe, so Al₆Fe is easy to be broken up and form the more stable Al₃Fe finally during aging. The addition of alloy elements changes the VES of Al₆Fe and makes its values of F, σ_N and n₁ increased, the stability of Al₆Fe is strengthened too, which delays the Al₆Fe→Al₃Fe transition and improves the transition temperature.