Home  About us  Contact
 

Surface Enrichment (surface + enrichment)

Distribution by Scientific Domains
Polymers and Materials Science71%

Selected Abstracts

Preparation and properties of organic,inorganic hybrid composites based on polystyrene and an incompletely condensed polyvinylsilsesquioxane oligomer

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010
Zhen Dai
Abstract An incompletely condensed polyvinylsilsesquioxane (PVSQ) oligomer containing abundant silanol groups was synthesized and characterized by FTIR, 1H-NMR, 29Si-NMR, and MALDI-TOF-MS. Polystyrene/polyvinylsilsesquioxane (PS/PVSQ) hybrid composites were prepared by an in situ bulk polymerization. The hybrid composites showed higher Tg, Td, and char yield than PS homopolymer and without mechanical loss. The improvements in the properties of PS/PVSQ hybrid composites can be ascribed to the crosslinking function of PVSQ by silanol condensation in later processing. The hybrids showed different morphology from discrete microstructure to continuous network depending on the concentration of PVSQ. Because of the surface enrichment, a PVSQ protection layer was formed, which made the hybrid surface more hydrophobic. The structure and the reaction mechanism of PS/PVSQ hybrid composites were also investigated. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Effect of potential on the corrosion behavior of a new titanium alloy for dental implant applications in fluoride media

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2004
A. M. Al-Mayouf
Abstract The effect of fluoride ion concentration and pH on the corrosion behavior of TCA (60 Ti 10 Ag 30 Cu), which is a new Ti alloy with low melting point, pure Titanium (Ti), and TAV (TiAl6V4) was examined using open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) at different potentials. Results show that the corrosion resistance of TCA and Ti decrease at anodic potentials compared with results obtained at OCP. At one potential the corrosion resistance decrease depends on NaF concentration and pH. TAV shows less resistance against corrosion in fluoride containing saliva. TCA has potentials more positive than Ti and TAV due to surface enrichment of Cu and Ag as Ti dissolves which accelerates the cathodic reaction. Fluoride ion may not hinder the growth of oxide layers on the surfaces of the electrodes. It will have influence on the properties of the oxide layer causing them to be not protective against corrosion in acid media containing fluoride ions. [source]

Growth kinetics of AlxGa1,xN layers (0 < x < 1) in plasma-assisted molecular beam epitaxy

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010
A. M. Mizerov
Abstract Comparative study of growth kinetics of the AlxGa1-xN (x = 0-1) layers of different polarity, grown by plasma assisted molecular beam epitaxy (PA MBE) under different growth conditions (substrate temperature, group III to activated nitrogen and Al to Ga flux ratios) and on different buffer layers, is presented. The 60 °C higher temperature stability of N-face AlGaN layers is detected. The strong influence of elastic stress on growth kinetics of metal-polar AlxGa1-xN (x > 0.2) layers is observed and discussed. It was found that two-dimensional growth of AlGaN films of the same composition on different buffer layers at TS = 700 °C can be achieved at different group III surface enrichment, the AlGaN(0001)/c-Al2O3 films exhibiting the atomically smooth surface at group III to activated nitrogen flux ratio FIII/FN *gradually increased from 1.3 to 2 with the x variation from 0.1 to 0.8. In this case the alloy composition is controlled by the variation of Al flux only (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Study of pseudo-multilayer structures based on starch-polycaprolactone extruded blends

POLYMER ENGINEERING & SCIENCE, Issue 6 2009
Laurent Bélard
This article is focused on the analysis of the structure-process relationships of biodegradable materials. It is mainly focused on the analysis of phase separation phenomenon occurring during the extrusion of plasticized starch/polycaprolactone blends, in a slit die. Rheological characterizations are carried out, in-line in an instrumented slit die at the exit of the extruder and, out-line with different rheometers. In certain conditions, a pseudo-multilayer structure can be generated with a polyester rich skin. Then, Electron Spectroscopy for Chemical Analysis (ESCA) and Fourier Transformed Infrared Attenuated Total Reflectance (FTIR-ATR) analyses are conducted to evaluate semi-quantitatively the polyester surface enrichment. In the range of available shear rates, the phase separation is mainly driven by the molecular weight of polycaprolactone, linked to its molten state viscosity. Three zones of surface enrichment, dependent on the molecular weights, are identified. Above 60,000 g·mol,1, no surface enrichment could be detected; below 37,000 g·mol,1, the phase separation occurs with no dependence on the processing conditions; between these two limits, the phase separation depends on both, the formulation and the processing conditions. A correlation between the rheological measurements and the phase separation is given. A predictive criterion based on the viscous behavior of the blend is established. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]

Structural, thermal, micromechanical and electrical study of polyimide composite thin films incorporating indium tin oxide

POLYMER INTERNATIONAL, Issue 9 2010
Anand Kumar Gupta
Abstract Studies of composite films incorporating inorganic materials are of immense importance for current technological applications. Polyimide (PI) composite thin films incorporating indium tin oxide (ITO) at various weight ratios were processed using an in situ generation approach. The resultant product was imidized up to 350 °C to test the ability of the material to endure high temperatures without affecting the host matrix. The morphological behaviour of the PI/ITO composite films was investigated using Fourier transform infrared, scanning electron microscopy and atomic force microscopy characterization techniques. The degrees of crystallinity and ITO particle size within the PI matrix were studied using X-ray diffraction. The thermal, structural and electrical properties were analysed using thermogravimetric analysis, differential scanning calorimetry, UV-visible spectroscopy and the four-probe technique. The micromechanical properties of the composites were evaluated in terms of tensile strength, tensile modulus and elongation. An overall improvement in the properties of the composite films was observed in comparison to those of pure PI. The synergistic improvement in the composite films is associated with the interaction mechanism between ITO and PI, where ITO becomes dispersed and interacts within the PI matrix. This leads to a decrease in available free-space volume and increases the surface enrichment providing reinforcement to the matrix. Copyright © 2010 Society of Chemical Industry [source]

Camouflage as Aesthetic Sustainability

ARCHITECTURAL DESIGN, Issue 6 2006
Dagmar Richter
Abstract A textile approach to architecture offers unique opportunities to explore a structure's surface and texture. Through a discussion of the history of the technique of camouflage and her own projects with Design Research and Development (DR_D), Dagmar Richter demonstrates the potential for surface enrichment to exceed mere ornament or patterning. A ,performative texture', camouflage interacts with its context mimicking the natural and effectively disguising whatever it covers. With a now long military association, camouflage also provides anything but a neutral background for its cover. Copyright © 2006 John Wiley & Sons, Ltd. [source]