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11.
S. Nagarajan 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(10):1800-1806
Results on photoluminescence and photostimulated luminescence studies of KBr1−xIx:TlI (0.01 and 0.05 mol%) mixed crystals grown in vacuum and air are presented. Photoluminescence spectra of the mixed crystals excited in the A-absorption band of KBr:Tl+ exhibited the characteristic emission bands of Tl+ ions in KBr:Tl+. When excited in the low energy tail of A-band absorption, additional emission bands were observed. Compared with earlier reports, excitation bands observed around 4.8, 4.6 and 4.4 eV are attributed to complex thallium centres of the form TlBr6−nIn (n = 0, 1, 2, 3). Photostimulated luminescence of γ-irradiated KBr1−xIx:TlI mixed crystals showed the presence of emission bands similar to the characteristic photoluminescence of Tl+ ions. The photostimulated luminescence slightly shifted towards the low energy side with increasing iodide composition x. The mechanism of emission in these mixed crystals is discussed. Dose response and storage stability (fading characteristics) in these mixed crystals are reported. 相似文献
12.
13.
Karthikeyan P. Mahadevan K. 《The International Journal of Advanced Manufacturing Technology》2015,80(9-12):1919-1926
The International Journal of Advanced Manufacturing Technology - This study attempts to incorporate SiC particles in the weld zone during friction stir welding of Al 6351 alloy. SiC particles of... 相似文献
14.
R.Elilarassi 《光电子快报》2010,6(1):6-10
Nanocrystalline undoped and nickel doped zinc oxide (Zn1-xNixO, x=0.00, 0.01) powders are successfully synthesized by a simple and low-temperature "auto-combustion method". The microstructural and optical absorption and emission properties of the as-prepared samples are obtained using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infra-red spectrometer (FTIR), UV-visible and photoluminescence (PL). The structure study confirms the formation of the hexagonal wurtz... 相似文献
15.
We demonstrate a simple, straightforward, clean-green, single pot approach for the synthesis of bimetallic Ag/Au nanoparticles (BNPs) by using a highly invasive terrestrial weed coral vine (Antigonon leptopus). Aqueous extracts of the weed were found to reduce the metal ions to form nanosised aggregates and then stabilise them by preventing further aggregation. The efficacy of the extracts of all its parts was explored by varying the stoichiometry of reactants, temperature, pH and reaction time. The electron micrographs of the synthesised BNPs indicated the presence of particles of predominantly spherical shapes in sizes ranging from 10 to 60 nm. The presence of gold and silver atoms was confirmed from the energy dispersive X-ray, X-ray photoelectron and X-ray diffraction studies. The Fourier transform infra-red spectroscopic spectral study indicated that the phenolics (including flavonoids) and proteins contained in the plant extract could have been responsible for the formation and stabilisation of the BNPs. 相似文献
16.
Audrey Hertz Yves-Marie Corre Stephane Sarrade Christian Guizard Anne Julbe Jean-Christophe Ruiz Bruno Fournel 《Journal of the European Ceramic Society》2010,30(7):1691-1698
The increasing interest of supercritical (SC) fluids for inorganic materials synthesis recently stimulated the development of innovative synthesis processes and strategies. The supercritical CO2 aided sol–gel process, developed for preparing various ceramic oxide powders with attractive applications in cosmetics, chromatography, catalysis or solid oxide fuel cells, usually suffer from both reproducibility problems and poor knowledge of the key parameters defining the final powder characteristics. In the present work a specific effort has been put on the understanding of reaction mechanisms and process parameters like co-solvent polarity and ageing time of the starting solution, which appeared to play a crucial role for the control of powder characteristics. Two different reaction mechanisms have been proposed to explain the formation of tetragonal yttria-doped zirconia powders by a batch process in either CO2/pentane or CO2/isopropanol mixtures. The first mechanism corresponds to a CO2 anti-solvent precipitation process while the other one is based on a condensation reaction as in the conventional sol–gel process. This improved understanding in particle formation allows better control of powder characteristics and reproducibility. 相似文献
17.
Parametric study on buckling behaviour of dented short carbon steel cylindrical shell subjected to uniform axial compression 总被引:2,自引:0,他引:2
Generally, thin cylindrical shells are susceptible for geometrical imperfections like non-circularity, non-cylindricity, dents, swellings, etc. All these geometrical imperfections decrease the static buckling strength of thin cylindrical shells, but in this paper only effect of a dent on strength of a short (Lc/Rc∼1, Rc/t=117, 175, 280) cylindrical shell is considered for analysis. The dent is modeled on the FE surface of perfect cylindrical shell for different angles of inclination and sizes at half the height of cylindrical shell. The cylindrical shells with a dent are analyzed using non-linear static buckling analysis. From the results it is found that in case of shorter dents, size and angle of inclination of dents do not have much effect on static buckling strength of thin cylindrical shells, whereas in the case of long dents, size and angle of inclination of dents have significant effect. But both short and long dents reduce the static buckling strength drastically. It is also found that the reduction in buckling strength of thin cylindrical shell with a dent of same size and orientation increases with increase in shell thickness. 相似文献
18.
《Food chemistry》2005,93(3):467-474
Novel biodegradable starch/clay nanocomposite films, to be used as food packaging, were obtained by homogeneously dispersing montmorillonite nanoparticles in different starch-based materials via polymer melt processing techniques. Structural and mechanical characterizations on the nanocomposite films were performed. The results show, in the case of starch/clay material, a good intercalation of the polymeric phase into clay interlayer galleries, together with an increase of mechanical parameters, such as modulus and tensile strength.Finally the conformity of our samples with actual regulations and European directives on biodegradable materials was verified by migration tests and by putting the films into contact with vegetables and simulants. 相似文献
19.
《Journal of power sources》2006,155(2):239-245
Experimental data show that heterogeneous nanostructure of solid oxide and polymer electrolyte fuel cells could be approximated as an infinite set of fiber-like or penny-shaped inclusions in a continuous medium. Inclusions can be arranged in a cluster mode and regular or random order. In the newly proposed theoretical model of nanostructured material, the most attention is paid to the small aspect ratio of structural elements as well as to some model problems of electrostatics. The proposed integral equation for electric potential caused by the charge distributed over the single circular or elliptic cylindrical conductor of finite length, as a single unit of a nanostructured material, has been asymptotically simplified for the small aspect ratio and solved numerically. The result demonstrates that surface density changes slightly in the middle part of the thin domain and has boundary layers localized near the edges. It is anticipated, that contribution of boundary layer solution to the surface density is significant and cannot be governed by classic equation for smooth linear charge. The role of the cross-section shape is also investigated. Proposed approach is sufficiently simple, robust and allows extension to either regular or irregular system of various inclusions. This approach can be used for the development of the system of conducting inclusions, which are commonly present in nanostructured materials used for solid oxide and polymer electrolyte fuel cell (PEMFC) materials. 相似文献
20.
The photoluminescence (PL) properties of singly doped (Dy3+) and codoped (Dy3+, Eu3+) fluoroaluminoborate glasses, with an emphasis on the white light generation, are studied. The γ-irradiation led to the formation of defects in Dy3+-doped glasses and photoreduction of Eu3+ to Eu2+ in codoped (Dy3+, Eu3+) glasses. The electron paramagnetic resonance spectra confirm the presence of divalent europium ions and defects in Dy3+, Dy3+–Eu3+-doped glasses. The FTIR spectra mainly establish the compaction of glass network due to γ-irradiation. From the PL spectra, the intensity ratio of Dy3+ emission bands yellow to blue (4F9/2–6H13/2/4F9/2–6H15/2) defines the site symmetry, covalency, and feasibility of extracting white light. The existence of an energy transfer (ET) from Dy3+ to Eu3+ ions are established due to the decrease in intensity of Dy3+ peaks with an increase of Eu2O3 content. Moreover, the non-exponential nature of decay curves was well fitted with the generalization of Yokota–Tanimoto model for electric dipole-quadrupole (S = 8) interaction that is responsible for ET process from sensitizer (Dy3+) to activator (Eu3+). 相似文献