Analytical approach à la Newmark for curved laminated glass

A method of solution that extends to the case of curved laminated structures the traditional approach developed by Newmark et al. for straight beams is presented. The method is specialized to curved laminated glass, a composite formed by two external glass layers that sandwich a very thin polymeric interlayer. The effect of curvature on the shear coupling of glass plies through the interlayer is examined in the paradigmatic example of a laminated beam with constant moderate curvature under radial loading with different boundary conditions, varying the initial camber, the end constraints and the elastic properties of the polymer. Comparisons with numerical experiments confirm the accuracy of the proposed modeling. In general the response of a curved structure is greatly influenced by the axial force it undergoes, and such internal action is mainly governed, for fixed applied loads, by the boundary conditions at the extremities. The axial force produces the arch-response of the structure, which is not substantially affected by the shear coupling of glass through the interlayer. On the other hand, such coupling has major effects on the bending properties.     

Enhanced visible green and 1.5 μm radiative emission of Er~(3+) ions in Li_2O-PbO-Al_2O_3-B_2O_3 glasses for photonic applications

A series of Er~(3+) ions doped lithium lead alumino borate(LiPbAlB) glasses were synthesized via melt quench method and their structural,physical and optical properties were studied.Judd-Ofelt theory in correlation with the emission and absorption profiles was performed for the measurement of various radiative parameters for different transitions of Er~(3+) doped glasses.The as-prepared glasses show deep green(550 nm) as well as NIR(1532 nm) emission at 380 and 980 nm excitation wavelengths,respectively.The intensity of emission spectra increases with Er~(3+) ions concentration up to 1.5 mol% and beyond quenching is observed.The Dexter theory applied to the emission profiles reveals the interaction between Er~(3+)ions as dipole-dipole in nature.CIE color coordinates are found to fall in the green region of the visible spectrum.It is observed that 1.5 mol% of Er~(3+) ions concentration is optimum to exhibit the maximum quantum efficiency,branching ratios,gain bandwidth,emission cross-section,gain crosssection and aptly suitable for visible and NIR photonic applications.     

热处理制度对玻璃金属封接行为的影响

本文借助光学显微镜观测手段,通过分析玻璃金属封接过程中平均孔径和孔隙率随封接温度和保温时间的变化,详细研究了热处理制度包括封接温度和保温时间对玻璃金属封接行为的影响。随着封接温度的升高,平均孔径先增大后减小,然而孔隙率先出现增加趋势,当封接温度高于980℃时基本则保持不变。随着封接时间的延长,平均孔径先逐渐增加后迅速降低,孔隙率则显著增加然后缓慢增加,接着迅速降低。另外,封接温度的提高和保温时间的延长都将导致无气泡带的变宽。本文根据封接热处理制度的变化,提出了一种空间气泡演变结构模型。     

Chemically dealloyed MgCuGd metallic glass with enhanced catalytic activity in degradation of phenol

Nanoporous Cu with tunable pore size (20–50 nm) are synthesized through chemical dealloying of the Mg₆₅Cu₂₅Gd₁₀ metallic glass in sulfuric acid solution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) demonstrated the formation of mixing structures consisting of amorphous matrix and fcc-Cu ligaments with nanoporous structure in the dealloyed samples. The nanoporous alloy obtained shows superior catalytic activity in degrading phenol-containing wastewater, e.g., the degradation rate increases by 2–4 times as compared to the un-dealloyed Mg-based metallic glass. It was also found that surface wettability plays an important role in degradation, which results in a better catalytic performance in the sample with coarser nanoporous structure although it has relatively less specific surface area as compared to the samples with finer pores. Finally, the mechanism for degradation of phenol is discussed.     

Elastic moduli and crosslinking of some tellurite glass systems

Tellurite glass systems in the form 80(TeO₂)–5(TiO₂)–(15 − x)(WO₃)–(x)A_nO_m have been prepared by the melt quenching technique. The A_nO_m oxide was Nb₂O₅ or Nd₂O₃ or Er₂O₃ and x ≤ 5 mol%. Density and Molar volume have been determined for the prepared glasses. Both longitudinal and shear ultrasonic velocities were measured in different compositions of the glass system by using the pulse-echo method at 5 MHz frequency and at room temperature. Ultrasonic velocity and density data have been used to calculate elastic moduli (longitudinal modulus L, shear modulus G, Young's modulus E, Bulk modulus K), Poisson's ratio σ, and Debye temperature θ_D. Quantitative analysis of elastic moduli based on the number of bonds per unit volume, average crosslinks and number of vibrating atoms per unit volume has been achieved.     

Luminescent properties of Cu+/Sn2+-activated aluminophosphate glass

A robust aluminophosphate glass matrix containing substantial amounts of Cu₂O and SnO has been prepared by the melt-quenching technique, and the luminescent properties have been assessed. The as-prepared material exhibits tunable luminescence by variation of excitation wavelength, in connection with the distinct excitation/emission properties of Cu⁺ ions and twofold-coordinated Sn centers in the host. Under excitation of both Cu⁺ and Sn species at 300 nm, the co-doped material exhibits a bright whitish luminescence, whereas excitation at 360 nm produces an intense orange emission arising merely from Cu⁺ ions. Thus, white light generation is deemed realizable by combination of cool-bluish emission intrinsic to Sn centers with the warm-orange emission from Cu⁺ ions. The optical properties of the material after heat treatment have been also investigated. Results indicate the chemical reduction of ionic copper via Sn²⁺ ultimately producing Cu nanoparticles as evidenced by the surface plasmon resonance. Consequently, the excitation-wavelength dependent photoluminescence bands appear suppressed in relation to Cu⁺ basically and show a dip attributed to light reabsorption by the plasmonic Cu particles.     

Effect of composite origin on magnetic properties of glass-coated microwires

We observed that magnetic properties (Giant magneto.-impedance effect and domain wall dynamic) of glass-coated microwires are closely related with the peculiarities of the fabrication technique involving rapid solidification of metallic alloy surrounded by glass coating from the melt.We present studies of the interfacial layer between the metallic nucleus and glass coating and studies of the inhomogeneities related with fabrication process of thin ferromagnetic microwires.We observed gas bubbles within the glass coating with volume content of about 8–12%. The sizes of the bubbles were between 1 and 15 μm. The existence of such bubbles might be the origin of the inhomogeneities in the internal stresses distribution.Using scanning electron microscope JEOL JSM-6610 we obtained the image of the interfacial layer and the elements distribution within the glass coating and metallic nucleus. This allowed us to estimate the thickness of the interfacial layer.Understanding of the origins of the interfacial layer and defects may help for improvement of the existing technology for thin composite wires fabrication and enhance their magnetic properties.     

Anisotropic nanocrystallization of a Zr-based metallic glass induced by Xe ion irradiation

Structural modification in a Zr-based metallic glass caused by irradiation with 7 MeV Xe²⁶⁺ ions was investigated. Needle-like nanocrystalline structures, formed under ion irradiation, consist of Cu₁₀Zr₇ phase (primary) and/or minor (Ni_xCu_1−x)₁₀Zr₇ phase. The formation of needle-like nanocrystals suggested an anisotropic atomic diffusion caused by ion irradiation.     

Origin of abnormal glass transition behavior in metallic glasses

In this paper, the phenomenon of two glass-transition-like appearance in the supercooled liquid region of metallic glasses was investigated. It is confirmed that this abnormal behavior is attributed to the transition process of an amorphous state from higher energy to lower energy. The amorphous state with higher energy comes from the uneven distribution of compositions in glasses, which is mainly caused by the component with significant differences in atomic size and nonnegative values of enthalpy of mixing. The results were verified by high resolution transmission electron microscopy and energy-dispersive spectrometry.