BUCKLING OF ANODIC FILMS ON ALUMINUM - DETERMINATION OF PLASTIC-DEFORMATION ENERGY OF COATINGS

The mechanical instability of oxide layers on anodized aluminum generates a regular arrangement of straight lines parallel to the cylindrical electrode axis. This is analyzed using Euler's equation for buckling of thin cylindrical shells under compressive forces, due to volume expansion concurrent with metal-oxide formation. The coating critical stress is determined as well as the energy dissipated by plastic deformation of the anodic coating. Most of the energy associated with compressive stress of the oxide film is dissipated by plastic deformation.14061667167

Structure imaging by atomic force microscopy and transmission electron microscopy of different light emitting species of porous silicon

The complex pattern of the nanowire skeletons of different light emitting porous silicon structures is investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Diffraction lines and dark field images are used to identify and determine the crystallite specimen long range order. TEM images give the size and particle orientation, and AFM images show a three-dimensional pattern formed by an interconnecting skeleton of particles. Near infrared photoluminescent porous silicon (0.005 Omega cm) structures show a skeleton of nanosized silicon aggregates which form domains of spatially oriented crystallites. For red photoluminescent samples (4.9 Omega cm) the electron diffraction spots are discontinuously split into tiny intensity maxima. The diameter of the wire structure forming porous silicon as measured by TEM allows us to estimate the distortion of the AFM images due to the finite size of the tip radius. A critical angle alpha(0)=2 arctan[K/(1 - K)](1/2), where K is the ratio of the height of the structure to the tip diameter was defined and it was shown that for structure walls steeper than alpha(0) the distortion may be substantial. (C) 1996 American Vacuum Society.1442432243

Scaling laws in annealed LiCoOx films

The surface morphology evolution due to the annealing process of LiCoOx thin films deposited by rf sputtering is studied by means of an atomic force microscope. Linear relationships were observed in log-log plots of interface width versus window length, as predicted by scaling laws. For as-grown films, only one growth exponent ais evidenced. For annealed films two different slopes alpha(1) and alpha(2) were observed, indicating distinct growth dynamics in the system. The roughness exponent for the as-grown film and the internal morphology of the crystalline grains for the annealed films can be described by a diffusional process. The macrostructure shows characteristics of a Kardar-Parisi-Zhang system [M. Kardar, G. Parisi, Y. C. Zhang, Phys. Rev. Lett. 56, 889 (1986); J. Krim and G. Palasantzas, Int. J. Mod. Phys. B 9, 599 (1995)]. An activation energy E-d = (0.11 +/-0.01) eV is determined for the diffusion process. (C) 1999 American Institute of Physics. [S0003-6951(99)02212-3].74121683168

Oxygen etching mechanism in carbon-nitrogen (CNx) domelike nanostructures

We report a comprehensive study involving the ion beam oxygen etching purification mechanism of domelike carbon nanostructures containing nitrogen. The CNx nanodomes were prepared on Si substrate containing nanometric nickel islands catalyzed by ion beam sputtering of a carbon target and assisting the deposition by a second nitrogen ion gun. After preparation, the samples were irradiated in situ by a low energy ion beam oxygen source and its effects on the nanostructures were studied by x-ray photoelectron spectroscopy in an attached ultrahigh vacuum chamber, i.e., without atmospheric contamination. The influence of the etching process on the morphology of the samples and structures was studied by atomic force microscopy and field emission gun-secondary electron microscopy, respectively. Also, the nanodomes were observed by high resolution transmission electron microscopy. The oxygen atoms preferentially bond to carbon atoms by forming terminal carbonyl groups in the most reactive parts of the nanostructures. After the irradiation, the remaining nanostructures are grouped around two well-defined size distributions. Subsequent annealing eliminates volatile oxygen compounds retained at the surface. The oxygen ions mainly react with nitrogen atoms located in pyridinelike structures. (C) 2008 American Institute of Physics.1031

Magnetic force images of nanomagnetic domains taken with platinum-coated tips

This article deals with magnetic force microscope images of nanosized domains in Co-coated films made by Pt-coated tips as well as micromagnetic images of data tracks written in recording media. Pt-coated tips have improved image delineation of the magnetic field distribution compared to images obtained by Co-coated hard magnetic tips. The force acting on Pt-coated tips in the magnetic field of the substrate was modeled assuming a paramagnetic tip. Due to the ferromagnetic nature of the interaction between the tip and substrate the spatial resolution of hard magnetic tips was shown to be inadequate to measure details of the features of nanosized domains. A comparison of the magnetic images made by Pt-coated tips with topographic images shows that magnetic domains resist thermal erasure at ambient temperature when they are formed of eight metallic grains. (C) 2003 American Institute of Physics.94162663

CHAOTIC BEHAVIOR OF CURRENT OSCILLATIONS DURING IRON ELECTRODISSOLUTION IN SULFURIC-ACID

Current oscillations vs time series were measured during iron electrodissolution in sulfuric acid solutions. The load line of the potentiostat was modified by an external resistance connected between the iron wire electrode and the potentiostat. The complex temporal behavior of these time series was diagnosed as deterministic chaos by the (i) reconstruction of the strange attractor, (ii) measurement of the Grassberger-Procaccia dimension (iii) calculation of the first Lyapunov exponent, and (iv) analysis of-the power spectra. In the anodic scan, oscillations start and stop with high values of Lyapunov exponent (greater than 40 bits/s). For the cathodic scan, the Lyapunov exponent increases as the potential increases. The calculated dimension varies between 1 and 3, for distinct values of potential and external resistances. The values of the dimension and the Lyapunov exponent decrease with the increasing of the external resistance. The route from periodicity (or quasi-periodicity) to chaos is probably related to the doubling at the period, with typical characteristics of a degenerated Hopf bifurcation.9948174031740

A NEW CURRENT INTERRUPTION TECHNIQUE DESIGNED FOR LARGE-AREA INDUSTRIAL ELECTROCHEMICAL-CELLS

13641011101

CETYLPYRIDINIUM CHLORIDE SORPTION IN AN ION-EXCHANGE RESIN - THE CASE OF SORPTION KINETICS ASSOCIATED WITH POLYMER FRACTURE

The adsorption of cetylpyridinium chloride (CPC) from aqueous solutions on a styrenic cation-exchange resin was determined, using dynamic (chromatographic) and static (batch) methods. Cation exchange site occupancy (theta) is less than 1% for short (100 s) contact times of surfactant solution with resin, but a approaches unity after 20-30 h, at the highest concentrations and temperatures used in this work. a vs time curves are not smooth and show surges of surfactant sorption, at some points. Microscopic examination showed that resin particles swell and break down during surfactant sorption, evidencing that the mechanical tensions created in this process are sufficient to induce fracture in highly cross-linked, poorly plasticized particles.1141347135

LARGE AREA INDUSTRIAL ELECTROCHEMICAL-CELLS TESTER

15749149