Materials Literature
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The study of poly( n -hexyl methacrylate) has been performed by both thermo-stimulated currents (TSC) and dynamic dielectric spectroscopy (DDS) in order to better define the nature of molecular mobility in the glass transition temperature range. TSC results reveal the existence of three dipolar relaxation modes: α, as…
Abstract The uncatalyzed cure of a commercial tetrafunctional epoxy monomer TGDDM ( N,N,N ′, N ′‐tetraglycidyl‐4,4′‐diaminodiphenylmethane) with hexahydrophthalic anhydride (HHPA), using variable stoichiometric ratios is reported. The reaction was followed by differential scanning calorimetry (DSC). Two kinds of exper…
This paper presents a physico-chemical and an electrical study of a low-density polyethylene used in cable insulation. The first part deals with the effect of temperature on morphology and the consequences on the conduction properties. Next, the influence of cross-linking by-products and antioxidant is studied. The an…
As part of a program to develop resins for high-performance/high-temperature aerospace structural applications, preliminary neat resin properties of naphthylethynyl terminated imide oligomers were determined and compared with the corresponding phenylethynyl terminated imide oligomers. Prior to oligomer work, four naph…
The diffusion coefficient of nickel nitrate dissolved in water in porous silica plates with different pore size was measured to investigate the effect of pore size on the liquid-phase diffusion resistance. The pore-diffusion coefficient of nickel nitrate varied with the pore size of the silica gel. In pores of diamete…
The first catalytic oxidation reactions with cofacial bisporphyrins using molecular oxygen as the terminal oxidant are presented. The photocatalytic reactions proceed under mild conditions (ambient temperature and pressure) without the need for a co-reductant. A systematic reactivity study of the photooxidation of dim…
Iron- and cobalt-exchanged ZSM-5 are active catalysts for the dissociation of nitrous oxide. In this study, density functional theory was used to assess a possible reaction pathway for the catalytic dissociation of N 2 O. The active center was taken to be mononuclear [FeO] + or [CoO] +, and the surrounding portion of…
Polyacrylonitrile/Na−MMT nanocomposites were synthesized through an emulsion polymerization of acrylonitrile (AN) using 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). The silicate (Na−MMT) layers were exfoliated during polymerization. The nanocomposites were exfoliated up to 20 wt % content of pristine Na−MMT re…
• The ability of the diatom Thalassiosira weissflogii to assimilate inorganic N in darkness is compared with that seen in flagellates. • Experiments were conducted with T. weissflogii grown in N-replete and in N-limiting cultures and the rates and capacity for ammonium and nitrate assimilation were determined. • High…
Abstract In this article, we report on recent investigations on filled natural rubber. These investigations include a mechanical characterization as well as a molecular analysis based on measurements of chain orientation. It is demonstrated that at intermediate strains, the increase in the moduli can be explained by t…
Charge-driven microencapsulation of water-soluble CdTe nanocrystals has been used to create both single-color tagged microspheres (see Figure) and multicolored beads with controlled emission intensity ratios. The concept is based on the pumping of negatively charged species into the interior of specially designed micr…
Nanoparticulate tungsten oxide films were synthesized by pulsed electrodeposition. Particle sizes between 45 and ∼330 nm were achieved by varying pulse duration from 5 to 500 ms. Shorter pulses increased the rate of new particle nucleation above the rate of existing particle growth, allowing for the observed variation…
We present photoluminescence studies as a function of temperature from a series of conjugated polymers and a conjugated molecule with distinctly different backbone conformations. The organic materials investigated here are: planar methylated ladder type poly para-phenylene, semi-planar polyfluorene, and non-planar par…
High-temperature superconductors are nowadays found in great variety and hold technological promise. It is still an unsolved mystery that the critical temperature T_c of the basic cuprates is so high. The answer might well be hidden in a conventional corner of theoretical physics, overlooked in the recent hunt for exo…
The strain generated by an actuator material when subjected to an external force is a key performance parameter. However, very little is known about the performance of polymer actuator materials when subjected to external loads. Increasing external loads were applied to polypyrrole films and the actuator response was…
Calculations of one-electron spectral functions, optical conductivity and spin-wave energy in the Holstein double-exchange model are made using the many-body coherent potential approximation. Satisfactory agreement is obtained with angle-resolved photoemission results on La_1.2Sr_1.8Mn_2O_7 and optical measurements on…
Semiconductor spintronics will need to control spin injection phenomena in the non-linear regime. In order to study these effects we have performed spin injection measurements from a dilute magnetic semiconductor [(Zn,Be,Mn)Se] into nonmagnetic (Zn,Be)Se at elevated bias. When the applied voltage is increased to a few…
A three-dimensional packed vesicular assembly was successfully prepared by using an organic-inorganic hybrid, the Cerasome. This assembly was achieved by using an alternate layer-by-layer adsorption technique with the anionic and the cationic Cerasome derived from corresponding organoalkoxysilane amphiphiles. Adsorpti…
To exploit the size dependent properties of nanoparticles, it is essential to control the particle size. We show that injection of octanethiol into suspensions of ZnO particles can be used to quench particle growth. X-ray photoelectron spectroscopy studies of the adsorption of octanethiol on ZnO single crystals indica…
Zeolitic wood structures made by a seeded templating process offer new ways of investigating the complex wood morphology. The technique can also be used to create hierarchical porous zeolitic materials (see Figure). The seeded growth strategy shows potential for the extension to any organisms with hierarchical structu…