Papers by Keyword: Gadolinium

Abstract: In this research we have studied contrast composition in the form of an aqueous solution containing gadolinium oxide (Gd₂O₃), diethylenetriaminepentaacetic acid (DTPA), medical polymer - polyvinylpyrrolidone mol. sq. (12000 ± 5000) daltons in an amount of 0.5-5 wt. %. To reduce the content of free gadolinium in the composition it has been suggested to change the stoichiometric ratio of the concentrations of DTPA/Gd₂O₃ in the mixture. The studies have shown that at a concentration ratio of DTPA/Gd₂O₃, 2.07 - 2.10 the impurity content of free gadolinium is at least 0.25%, which is significantly below the regulated value - 0.5%. The conducted biomedical tests have confirmed the functionality of the resulting contrast composition.

Abstract: Pure Mg and AZ91D alloy was anodized with and without the gadolinium nitrate Gd (NO₃)₃ in different concentrations (0.001g/l, 0.025g/l, 0.05g/l, 0.075g/l and 0.09g/l) at a constant current density and treatment time of 10mA/cm² and 5 minutes. The results showed that the optimum gadolinium concentration is 0.075g/l due to obtaining the anodic film with high corrosion resistance. The surface morphology and microstructure of anodic coating were investigated by scanning electron microscopy (SEM) , optical microscope (OM), and potentiodynamic polarization, respectively.

Abstract: An experimental method is suggested for the determination of the rate of magnetic phase transitions. The method is based on the measurement of the change of magnetic susceptibility of a ferromagnetic sample in the vicinity of the phase transition in response to an abrupt change of the sample temperature. This paper describes the measurement of the change of the magnetic susceptibility of a thin gadolinium plates, cooled by water-flow at a temperature below the Curie point (T_C=292 K). It was found that the relaxation time of the magnetic susceptibility of gadolinium in the temperature range from 289.9 to 291.3 K can be approximated using the Landau-Khalatnikov equation with a kinetic coefficient value γ = 3.9×10^-8 cm³/(erg×s). The linear approximation does not fit well in the range from 291.3 to 293.2 K. The fundamental restriction of specific power of the magnetocaloric refrigerator (made by gadolinium plates) was estimated.

Abstract: Gadolinium–doped ZnO nanocrystalline powders were prepared by hydrothermal method using ionic liquid (1-heptyl-3-methyl imidazole bromide) as template. The crystal structure, grain size and optical properties of the samples were characterized by X-ray diffractometry, scanning electron microscopy and UV-Vis spectroscopy. The photocatalytic degradation of KN-R dye under simulated sunlight was chosen as a model reaction to evaluate the photocatalytic activities of the undoped and doped ZnO nanocrystalline catalysts. It was shown that Gadolinium was successfully doped into ZnO powders, and thus showing enhanced performance in degradation of KN-R.

Abstract: The effect of Gd addition on the microstructures and mechanical properties of Mg-5Sn-Zn-Al alloy was investigated with variations of Gd contents. These results show that adding Gd can effectively refine the grain size and growth. In addition, the solubility of Gd increases the lattice constants of α-Mg phase. Accordingly, the tensile properties of the as-cast Mg-5Sn-Zn-Al alloy are improved by the addition of Gd. The Mg-5Sn-Zn-Al-0.4Gd exhibits the highest tensile properties, and the values of the yield and ultimate tensile strength and elongation are 111 MPa, 188 MPa and 18.0%, respectively.

Abstract: A new chemiluminescence system was built by using gadolinium as sensitizer, and the analysis capabilities of this system was tested as below. The method is based on chemluminescence of Ce (IV)-SO₃^2- sensitized by Gd³⁺-OFLX. The effects of some critical experimental conditions were discussed and the optimum conditions for chemluminescence emission were investigated. The linear relationship between the relative chemiluminescence intensity and the concentration of OFLX is in the range of 2×10^-9 g/mL～5×10^-7 g/mL with a detection limit of 1.0×10^-9g/mL .The relative standard deviation is 2.8% (n=11) for a level of 5.0×10^-7 g/mL. The method has been applied to the analysis of OFLX in tablets with satisfactory results.

Abstract: The effect of micro-and nanocrystalline structural state on magnetic properties and magnetic entropy (ΔS_M) of Gd is investigated. The marked influence of severe plastic deformation on ΔS_M is demonstrated.

Abstract: Pure BiVO₄, single doped and co-doped BiVO₄ have been prepared by chemical precipitation method and characterized by the techniques such as XRD and SEM/EDAX. The photocatalytic degradation of methylene blue (MB) in aqueous solution was used as a probe reaction to evaluate pure BiVO₄, single doped BiVO₄ and co-doped BiVO₄ photocatalytic activity. The results show that doping of single doped and co-doped significantly enhance the photocatalytic activity of BiVO₄. When the 0.1%Gd³⁺ and 0.2%Sm co-doped, the BiVO₄ degradation rate reaches 91%.

Abstract: Magnesium (Mg) is a hexagonal close-packed light metal whose deformation re-sponse is characterized predominantly by easy slip on the f0002g basal plane at temperaturesbelow 200°C. Rolled sheet products develop a strong basal texture and become \plasticallychallenged" in subsequent forming operations. In the literature, additions of rare earth ele-ments (REE) to Mg have inconsistently reported non-basal texture formation. In this work,Mg-0.2wt%Gd and 0.2-wt%La were investigated to determine whether the presence of theseelements contributed to non-basal texture formation after elevated temperature plane straincompression. Test specimens were prepared from book-mould castings after homogenization at400°C, and reduced 50% in a channel die at 250, 325, or 375°C and 10^-2/s. The stress-strainbehaviours were all characterized by apparent twin-related softening, followed by monotonichardening to the end of the imposed deformation. The yield stress for Mg-0.2%La (15-22 MPa)was higher and less temperature dependent than for Mg-0.2%Gd (10-18 MPa). Texture mea-surements indicate the spread of ideal basal texture about TD with increased temperature, butalso also greater non-basal textures in the Mg-0.2%Gd alloy, particularly at 325°C. Electronchanneling contrast imaging revealed a more re ned and homogeneous substructure in the Gd-containing alloy compared with larger microbands in the La-containing alloy, and suggests thatcontinuous recovery and other available slip systems may contribute to these di erences.

Abstract: The effect of Gd(gadolinium) on the microstructure and mechanical properties of aged AZ81 magnesium alloy were investigated. The results showed that 2wt.%Gd addition results in the obvious refinement of grain size, the decrease of β-Mg₁₇Al₁₂ phase and the formation of Al₂Gd phase, and improves the mechanical properties of AZ81 alloy at room and high temperature. After the addition of 2wt.%Gd, the tensile strengths are enhanced from 203.2MPa to 249.3MPa at room temperature and from 157.2MPa to 197.3MPa at 150°C. Meanwhile, the elongations are increased.