Materials Literature
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We study the brittle fragmentation of spheres by using a three-dimensional discrete element model. Large scale computer simulations are performed with a model that consists of agglomerates of many particles, interconnected by beam-truss elements. We focus on the detailed development of the fragmentation process and st…
The origin of helicity asymmetries in the optically-pumped NMR signal and hyperfine shift in GaAs is derived analytically and tested experimentally. The ratio of the optically-pumped to the equilibrium electron polarizations is a key parameter in determining both asymmetries. Variations in asymmetry with photon energy…
In this paper, we introduce a unique method for fabricating $\mathrm{Mg}{\mathrm{B}}_{2}∕\mathrm{Mg}\mathrm{O}$ multilayers and demonstrate the potential for using them as a new model for disordered superconductors. In this approach, we control the annealing of the $\mathrm{Mg}{\mathrm{B}}_{2}$ to yield an interesting…
A reverse microemulsion method is reported for preparing monodispersed silica-coated gold (or silver) nanoparticles without the use of a silane coupling agent or polymer as the surface primer. This method enables a fine control of the silica shell thickness with nanometer precision. As compared to the Stöber method re…
We predict general trends for surface segregation in a binary metal cluster based on the difference between the atomic properties of the constituent elements. Considering the attractive and repulsive contributions of the cohesive energy of an atom in a cluster, energetically most favorable sites for a guest atom on a…
This contribution reports on comparative studies on giant magnetoresistance (GMR) in carbon nanotubes (CNTs) and graphene nanoribbons of similar aspect ratios (i.e perimeter/length and width/length ratios, for the former and the latter, respectively). The problem is solved at zero temperature in the ballistic transpor…
We theoretically calculate and compare the single particle relaxation time $({\ensuremath{\tau}}_{s})$ defining the quantum level broadening and the transport scattering time $({\ensuremath{\tau}}_{t})$ defining the Drude conductivity in two-dimensional (2D) graphene layers in the presence of screened charged impurity…
Abstract Composites made with boron might be absorbers of low energy neutrons, and could be used for structural materials for spacecraft. Polyethylene/boron nitride composites were fabricated using conventional polymer processing techniques, and were evaluated for mechanical and radiation shielding properties. The bor…
Abstract The structural changes of aniline oligomers and polyaniline, associated with oxidation of aniline with ammonium peroxydisulfate in aqueous solutions without any added acid, were studied. The reaction was quenched at various times and the films deposited on silicon windows have been studied in detail by Raman…
The Josephson effect and superconducting proximity effect were observed in superconductor-graphene-superconductor (SGS) Josephson junctions with coherence lengths comparable to the distance between the superconducting leads. By comparing the measured gate dependence of the proximity induced subgap features (multiple A…
Silicon (Si) quantum dot (QD) materials have been proposed for 'all-silicon' tandem solar cells. In this study, solar cells consisting of phosphorus-doped Si QDs in a SiO(2) matrix deposited on p-type crystalline Si substrates (c-Si) were fabricated. The Si QDs were formed by alternate deposition of SiO(2) and silicon…
Extensive calculations based on density functional theory have been carried out to understand the origin of magnetism in undoped ZnO thin films as found in recent experiments. The observed magnetism is confirmed to be due to Zn, instead of O, vacancy. The main source of the magnetic moment, however, arises from the un…
With octahedral Au nanocrystals as seeds, highly monodisperse Au@Pd and Au@Ag core-shell nanocubes were synthesized by a two-step seed-mediated method in aqueous solution. Accordingly, we have preliminarily proposed a general rule that the atomic radius, bond dissociation energy, and electronegativity of the core and…
The aim of this study was to use a life-cycle perspective to model the quantities of engineered nanoparticles released into the environment. Three types of nanoparticles were studied: nano silver (nano-Ag), nano TiO2 (nano-TiO2), and carbon nanotubes (CNT). The quantification was based on a substance flow analysis fro…
Abstract A new chemical modification of liquid polybutadiene by radical addition of model aldehydes (butanal and hexanal) onto pending vinyls of the polymer is described. The dibenzoyl peroxide/N,N‐dimethylaniline redox system was shown to initiate the hydroacylation more efficiently than the thermal decomposition of…
Clostridial glutamate dehydrogenase mutants with the 5 Trp residues in turn replaced by Phe showed the importance of Trp 64 and 449 in cooperativity with glutamate at pH 9. These mutants are examined here for their behaviour with NAD+ at pH 7.0 and 9.0. The wild-type enzyme displays negative NAD+ cooperativity at both…
Pb–C nanocomposites consisting of pyrolytic carbon nanospheres and Pb nanoparticles were produced by discharging a mixture of Pb and graphite powders in an ethanol and Ar atmosphere. Raman spectrum and x-ray photoelectron spectroscopy indicated that the carbons in the Pb–C nanocomposites are in both ordered and disord…
Abstract Crosslinked networks were synthesized by copolymerization of mono‐functional tert‐butyl acrylate (tBA) with diethyleneglycol dimethacrylate (DEGDMA) or polyethylene glycol dimethacrylates (PEGDMA). By varying the chain length and concentration of the difunctional PEGDMA, we obtained tBA‐PEGDMA copolymer netwo…
ZnO is a wide and direct band-gap material (3.37 eV at room temperature) making this compound very suitable for UV photodetector applications as well as for UV and blue light emitting devices. As an electronic conductor, ZnO may be used as transparent and conducting electrodes for flat panel displays and solar cells.…
By using quasielastic neutron scattering (QENS) with isotopic labeling we have investigated the component dynamics in a miscible blend of polyethersulfone (PES) and poly(ethylene oxide) (PEO) with 75% content in weight of PES. Due to the large difference in the glass-transition temperatures, T(g)'s, of the two polymer…