Materials Literature
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Surface-enhanced Raman scattering (SERS) of adsorbed molecules on gold nanorods (NRs) with dimensions of 10 nm × 27 nm was studied on silica surface with low to high surface coverage of NRs. The study was carried out to investigate both the dependence of the SERS intensity on the number of NRs and the NRs spacing on t…
We present a simple analytical model for the forces that determine jet diameter during electrospinning as a function of surface tension, flow rate, and electric current in the jet. The model predicts the existence of a terminal jet diameter, beyond which further thinning of the jet due to growth of the whipping instab…
In this paper we present the results of a study of the effect of high-temperature stress annealing in nitrogen on the index of refraction of SiO<sub>2</sub> layers in MOS (metal/oxide/semiconductor) devices. The dependence of mechanical stress in the Si-SiO<sub>2</sub> system on the annealing conditions has been exper…
A novel approach to the teaching of material to engineering students is outlined. It starts from the overview of the "world" of materials made possible by material property charts, and develops both an understanding of material properties and skills in selecting materials and processes to meet design specifications. I…
In this paper tuneable optical filters based on liquid crystal Fabry-Perot interferometers (LCFPI) are presented. Liquid crystal (LC) devices are lightweight and suitable for compact arrays with a large number of pixels, as shown in high resolution flat panel displays. The fabricated filters offer a high finesse (119)…
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It is established by using Co-Mo model sulfide catalysts, XAFS and FTIR that Co atoms constituting CoMoS phases are not oxidized by NO adsorption and that only 55% of the CoMoS phases is susceptible to NO adsorption even at the maximum coordinative unsaturation attainable under usual HDS reaction conditions (623-673 K…
The generation of surface anisotropy by photochemical means has been proposed as an attractive method to align liquid crystals. In this paper, we present an experimental study of the alignment induced on a liquid crystal by a polymer film containing azo-dye groups in the side chain. Optical measurements were performed…
The paper provides details on the structure and implementation of the Computational Materials program at the NASA Langley Research Center. Examples are given that illustrate the suggested approaches to predicting the behavior and influencing the design of nanostructured materials such as high-performance polymers, com…
Nucleophilic substitution reaction of poly(3-hexylthiophene) (P3HT) with pyridine derivatives as nucleophile was demonstrated in anodic oxidation process. The key reaction involves efficient nucleophilic attack of the pyridine derivatives toward thiophene rings in partly oxidized polymer, i.e., doped state, in the sim…
Rietveld refinement of powder neutron diffraction data, combined with group theory considerations, is used to determine the magnetic structures of the binary metal dicyanamide, ${M}^{\mathrm{II}}[{\mathrm{N}(\mathrm{CN})}_{2}{]}_{2}$ where $M=\mathrm{Ni},$ Co, Fe, Mn, ${\mathrm{Ni}}_{0.5}{\mathrm{Co}}_{0.5},$ and ${\m…
When the real parts of the permittivity and the permeability dyadics of a structurally chiral, magnetic-dielectric material are reversed in sign, the circular Bragg phenomenon displayed by the material is proved here to suffer a change which indicates that the structural handedness has been, in effect, reversed. Addit…
In this work we undertake the problem of a transition metal impurity in an oxide. We present an ab initio study of the relaxations introduced in ${\mathrm{TiO}}_{2}$ when a Cd impurity substitutionally replaces a Ti atom. Using the full-potential linearized-augmented-plane-wave method, we obtain relaxed structures for…
We study numerically the electromagnetic scattering properties of structures with negative indices of refraction. To perform this analysis, we utilize a commercial finite-element based electromagnetic solver (HFSS, Ansoft), in which a negative index material can be formed from mesh elements whose permittivity and perm…
The oxidation of 5,15-bis(3,5-di-tert-butylphenyl) Ni(II)-porphyrin 1b with Sc(OTf)3 and DDQ led to production of meso-beta doubly linked Ni(II)-porphyrin tapes that have large pi-electronic communications over the arrays.
We report on the development and use of a highly anisotropic magnetic metamaterial for near-field imaging. The material consists of an array of Swiss Roll structures, resonant near 21.3 MHz, with a peak value of relative permeability ~35. At this peak, the material transfers an input magnetic field pattern to the outp…
We have previously shown that a new class of Negative Refractive Index (NRI) metamaterials can be constructed by periodically loading a host transmission line medium with inductors and capacitors in a dual (high-pass) configuration. A small planar NRI lens interfaced with a Positive Refractive Index (PRI) parallel-pla…
We investigated a precursor of superlensing: regenerating evanescent waves by excitation of a surface plasmon. Because the permittivity of a silver slab approaches -1, we experimentally observed a broadening of surface-plasmon bandwidth. Our study identifies a means to access deep subwavelength features by use of a me…
The mathematical solution for Cerenkov radiation in a novel medium, left-handed medium (LH medium), which has both negative permittivity and permeability, is introduced in this paper. It is shown that the particle motion in the LH medium generates power that propagates backward. In this paper, both dispersion and diss…
In the material SmLa$_{1-x}$Sr$_x$CuO$_{4-δ}$ with alternating intrinsic Josephson junctions we explain theoretically the relative amplitude of the two plasma peaks in transmission by taking into account the spatial dispersion of the Josephson Plasma Resonance in $c$ direction due to charge coupling. From this and the…