Here we report the fabrication of high conductive and large surface-area 3D pillar graphene nanostructures (PGN) films from assembly of vertically aligned CNT pillars on flexible copper foils and directly employed for...
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Broadband fluorescence and fluorescence line narrowing (FLN) spectra are presented for Eu3+ ions in Eu2O3-SiO3 and Eu2O3-Al2O3-SiO3 systems prepared by the sol-gel process. Clustering of rare earth ions in silica glas...
Broadband fluorescence and fluorescence line narrowing (FLN) spectra are presented for Eu3+ ions in Eu2O3-SiO3 and Eu2O3-Al2O3-SiO3 systems prepared by the sol-gel process. Clustering of rare earth ions in silica glass can be a limiting factor in the design and engineering of optical device materials. The addition of Al2O3 is known to help disperse rare earth ions in sol-gel silica. In order to develop a more detailed understanding of how Eu3+ is incorporated in these materials, time-resolved, laser-induced FLN studies at 77 K have been performed using a pulsed dye laser to selectively excite subsets of ions in the inhomogeneously broadened7F0↔ 5D0 manifold. Fluorescence spectra are discussed in terms of rare earth ion clustering, energy transfer, and bonding site symmetry. It is concluded that Eu3+ ions cluster in sol-gel silica and that the addition of alumina assists in dispersing Eu3+ ions.
This paper demonstrates that Sequential Lateral Solidification (SLS) of Si can be carried out on films as thin as–and potentially much thinner than–250 Å. When compared to thicker Si films, however, the SLS-pro...
This paper demonstrates that Sequential Lateral Solidification (SLS) of Si can be carried out on films as thin as–and potentially much thinner than–250 Å. When compared to thicker Si films, however, the SLS-processed ultra-thin films contain more twins, and successful processing requires irradiation within a narrower laser energy density range and a smaller per-pulse translation distance. The physical interpretation of these findings is formulated by analyzing the details of the microstructures observed in single-pulse-irradiation-induced Controlled Super-Lateral Growth (C-SLG) experiments. SEM and TEM analyses reveal complicated microstructural details that we interpret as originating from breakdown of epitaxial growth during lateral solidification, an effect that is detrimental to the SLS process. Based on considerations of far-from- equilibrium solidification behavior of Si, it is argued that undercooling of the solidification interface below a threshold value at which solidification no longer proceeds epitaxially–arising from reduction in interfacial recalescence during lateral solidification of ultra-thin Si films, relative to that of thicker films–is responsible for the breakdown. Based on this model, we discuss how external parameters may be adjusted so as to permit optimal crystallization of ultra-thin Si films using SLS.
The magnetic properties, structural properties, and thermal conductivity of FePt films deposited on Ag and Cu heat sink layers designed for use in heat-assisted magnetic recording (HAMR) were investigated. It has been...
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This work quantifies the influence of nonlinear elasticity on the accuracy of the thermal shock damage evaluation of highalumina refractory castables based on dynamic Young's modulus and damping characterization d...
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This work quantifies the influence of nonlinear elasticity on the accuracy of the thermal shock damage evaluation of highalumina refractory castables based on dynamic Young's modulus and damping characterization data obtained via the impulse excitation technique (IET).The nonlinear elasticity leads to shifts in the Young's modulus and damping values in dependence of the impulse intensity. An IET apparatus was employed according to the ASTM E1876-07 standard;the method was improved by nonlinear analysis based on the excitation control. Two arbitrary coefficients were defined to evaluate the nonlinearity with respect to the impulse intensity. Three high-alumina refractory castables were submitted to progressive thermal shock damage and evaluated. The results show that the influence of nonlinear elasticity on the Young's modulus is significant and that nonlinear elasticity is a determining factor for the accuracy of the damping characterization (up to -0.93 % and +114 %, respectively, depending on the damage level).
We describe the fabrication of highly sensitive graphene based field effect transistor (FET) biosensors with a cost-effective approach and their application in label-free Deoxyribonucleic acid (DNA) detection. Chemica...
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Single-phase Ba(Cd1/3Ta2/3)O3 ceramics have been produced using conventional powder processing methods. In our initial investigations, 2wt% ZnO powder was added to act as a sintering aid since a high-density ceramic w...
Single-phase Ba(Cd1/3Ta2/3)O3 ceramics have been produced using conventional powder processing methods. In our initial investigations, 2wt% ZnO powder was added to act as a sintering aid since a high-density ceramic was not formed from solid-state diffusion alone. The resulting Ba(Cd0.327Zn0.006Ta2/3)O3 material sintered at 1550° C exhibits a dielectric constant of ∼33 and loss tangent of <5×10−5 at 2 GHz. In our more recent work, we have used boron as a sintering aid to facilitate sintering at temperatures as low as 1300° C, enhance the structural quality and improve the microwave properties of Ba(Cd1/3Ta2/3)O3 dielectrics. TEM results indicate that the liquid sintering mechanism is an important factor for boron concentrations exceeding 0.5wt%, while a point defect mechanism plays the dominant role at lower boron concentrations. The presence of superstructure peaks and splitting of the (220) and (214) peaks in X-ray diffraction spectra are direct evidence for the distortion from cubic symmetry as a result of Cd and Ta ordering on the ***-initio electronic structure calculations within the local density functional approximation have been used to give insight into the unusual properties of this class of materials. In both Ba(Zn1/3Ta2/3)O3 and Ba(Cd/3Ta2/3)O3, the conduction band maximum and valence band minimum are composed of mostly weakly itinerant Ta 5d-and Zn-3d/Cd-4d levels, respectively. The covalent nature of the directional d-electron bonding in these high-Z oxides plays an important role in producing a more rigid lattice with higher melting points and enhanced phonon energies, and possibly inherently lower intrinsic microwave loss than comparable ionic materials.
A numerical model of an experimental gallium nitride horizontal vapor phase epitaxy reactor is presented. The model predicts the flow, concentration profiles, and growth rates. The effects of flowrate variation and ge...
A numerical model of an experimental gallium nitride horizontal vapor phase epitaxy reactor is presented. The model predicts the flow, concentration profiles, and growth rates. The effects of flowrate variation and geometry on the growth rate, growth uniformity and crystal quality were investigated. Numerical model predictions are compared to experimentally observed values. Parasitic gas phase reactions between group III and group V sources and deposition of material on the wall are shown to lead to reduced overall growth rates and inferior crystal quality. A low ammonia concentration is correlated to deposition of polycrystalline films. An optimum HVPE growth process requires selection of reactor geometry and operating conditions to minimize parasitic reactions and wall deposition while providing a uniform reactant distribution across the substrate.
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