Materials Literature
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The cell wall (frustule) of the freshwater diatom Pinnularia viridis (Nitzsch) Ehrenberg is composed of an assembly of highly silicified components and associated organic layers. We used atomic force microscopy (AFM) to investigate the nanostructure and relationship between the outermost surface organics and the silic…
Abstract Conditions were established for dispersing clay nanolayers into both cis ‐1,4‐polyisoprene (synthetic) natural rubber (NR) and epoxidized natural rubbers (ENR) having 25 or 50 mol % epoxide. The clay was a sodium montmorillonite and was used as a pristine layered silicate or as organically modified layered si…
LaMnO(3) was studied by synchrotron x-ray diffraction, optical spectroscopies, and transport measurements under pressures up to 40 GPa. The cooperative Jahn-Teller (JT) distortion is continuously reduced with increasing pressure. There is strong indication that the JT effect and the concomitant orbital order are compl…
First-principles electronic structure calculations of cerium oxide in two forms, ${\mathrm{CeO}}_{2}$ and ${\mathrm{Ce}}_{2}{\mathrm{O}}_{3},$ are presented. The $4f$ state of Ce is treated as a part of the inner core in ${\mathrm{Ce}}_{2}{\mathrm{O}}_{3}$ and as a valence-band-like state in ${\mathrm{CeO}}_{2}.$ The…
This paper describes an electrostatic field-assisted assembly technique combined with an electrospinning process used to position and align individual nanofibres (NFs) on a tapered and grounded wheel-like bobbin. The bobbin is able to wind a continuously as-spun nanofibre at its tip-like edge. The alignment approach h…
Analizamos las fracciones de fitoplancton y bacterioplancton en tres ecosistemas lénticos (los embalses de Neusa y Prado y la laguna de Fúquene), con características fisicoquímicas distintas, a fin de verificar el acoplamiento entre estas comunidades. Las muestras se tomaron en tres sitios de cada cuerpo de agua, en t…
The effect of surface roughness on electron emission from hydrogenated polycrystalline diamond films is reported. Field emission measurements were performed with both millimeter and nanometer spatial resolution using scanning probe techniques. Surface asperities were removed by ion beam treatment, which resulted in a…
Large arrays of self-oriented, multiwalled carbon nanotubes (MWNTs) have been obtained by chemical vapor deposition. It has so far been impossible to translate this idea for growing single walled nanotubes (SWNTs) but we show here that oriented growth of SWNTs among vertically aligned MWNT arrays can be realized by th…
We report observation of the Coulomb blockade effect in a metal-on-tube metal/multiwall carbon nanotube (MWNT)/metal structure (metal=Ti or Pt/Au). We find that the tunnel barrier is located in the interface between the MWNT and the metal electrode, and that the tunnel resistance depends crucially on the electrode mat…
We use field effect doping to study both electron- (n) and hole- (p) type conduction in a semiconducting carbon nanotube. We find that, in the n-type region, the ends of the tube remain p- type due to doping by the metal contacts. As a result, a p–n junction forms near the contact, creating a small, p-type quantum dot…
Magnitudes of strain in ZnO epitaxial layers grown on sapphire(0001) substrates under various growth conditions were experimentally determined by x-ray diffraction. We discuss the strain-induced energy shift on the exciton resonances, the results of which were analyzed theoretically using the Hamiltonian for the valen…
Experimental studies of size-related effects in silicon nanocrystals are reported. We present investigations carried out on nanocrystals prepared from single-crystal Si:P wafer by ball milling. The average final grain dimension varied depending on the way of preparation in the range between 70 and 230 nm. The ball mil…
We have investigated the processing and properties of La2/3Ca1/3MnO3 self-assembled nanodots formed in a nonmagnetic alumina matrix, which were produced by a pulsed-laser deposition process. The size of the nanodots was found to be in the range of 10–15 nm using high-resolution transmission electron microcopy. The ave…
Cavity-QED studies in a low-Q regime demonstrate enhanced spontaneous emission from CdSe/ZnS core/shell nanocrystals embedded in a polystyrene microsphere and provide important information on radiative dynamics in these quantum dots. The cavity-induced relative enhancement in photoluminescence decay rates depends sens…
A void formation mechanism was investigated in an electroplated copper thin film on Ta/SiO2/Si. Microstructural observation after thermal cycling indicated that void formation occurred at intersecting points or terminating corners of annealing twins. The calculated stress distribution was compared with experimental re…
The magnetocaloric effect has been investigated in a series of the R5(SixGe1−x)4 pseudobinary alloys with R=Tb and x=0.0, 0.5, and 1.0. In Tb5Si4 and Tb5Ge4, a maximum magnetic entropy change of 9.8 and 3.7 J/kg K, respectively, has been found at their ordering temperatures for a magnetic field change of 50 kOe. In th…
CoPt/Ag nanocomposites with the tetragonal (L10) structure have been prepared by magnetron sputtering. The dependence of texture on film thickness, bilayer thickness, CoPt volume fraction, and annealing conditions is investigated. Films with a thickness below 15 nm consist of islands with (001) texture while as the th…
A variational principle is proposed that allows to derive the equations of motion for a fluid with a general microstructure described by a tensorial order parameter. The only constitutive ingredients are the densities of the free energy and the dissipation, both subject to appropriate invariance requirements. As an il…
Energy-filtered transmission electron microscopy is used to image the nanocomposite FeAl+Y2O3, an oxide-dispersion-strengthened intermetallic alloy, over a tilt range of ±60° using inelastically scattered electrons only. The properties of electron spectroscopic imaging are exploited to recover a projection relationshi…
We have investigated the effect of surface order on the orientation and mobility of pentacene. The surface order was created using monolayers and polymers that are normally used to align liquid crystals. Rubbed polyvinylalcohol layers were found to align approximately 27% of the pentacene grains within a 30° range. Wh…