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Precursor Films (precursor + film)

Distribution by Scientific Domains
Polymers and Materials Science75%

Selected Abstracts

Direct Correlation of Organic Semiconductor Film Structure to Field-Effect Mobility,

ADVANCED MATERIALS, Issue 19 2005
M. DeLongchamp
Near-edge X-ray fine structure spectroscopy is used to measure simultaneous chemical conversion, molecular ordering, and defect formation in soluble oligothiophene precursor films. Film structure is correlated to OFET performance. Molecular orientation is determined by evaluating antibonding orbital overlap with the polarized electric field vector of incident soft X-rays (see Figure and cover). Upon conversion, the molecules become vertically oriented, allowing , overlap in the plane of hole transport. [source]

Crystallization, orientation morphology, and mechanical properties of biaxially oriented starch/polyvinyl alcohol films

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008
Jing Wang
Abstract Biaxially oriented starch/polyvinyl alcohol (PVA) films were prepared by stretching starch/PVA blend precursor films that were fabricated by extrusion casting via a twin-screw extruder. Investigations on crystallization, orientation morphology, and mechanical properties of extrusion cast and stretched starch/PVA films were carried out by using differential scanning calorimetry, scanning electron microscope, wide angle X-ray diffraction (WAXD), and tensile testing. The fresh extrusion-cast starch/PVA films, which were almost amorphous, can crystallize spontaneously when aged at room condition. A good compatibility between starch and PVA was obtained by extrusion-casting technology. The well-developed molecular orientation, which did not occur along the machine direction during the extruding process, was observed in stretched film samples. Stretching unaged films can induce crystallization and the orientation of crystalline structures during stretching, resulting in the changes in diffraction peaks of WAXD patterns. The effect of stretch ratio and the orientation distribution in the plane of the film on mechanical properties of stretched films was studied, and the equal biaxially oriented films were found to exhibit in-plane isotropy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

Influence of the stacking order on structural features of the Cu-In-Ga-Se precursors for formation of Cu(In,Ga)Se2 thin films prepared by thermal reaction of InSe/Cu/GaSe alloys to elemental Se vapor and diethylselenide gas

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2006
F.B. Dejene
Abstract A novel partway for the fabrication of copper-indium (gallium) diselenide has been developed. This two-stage process consists of the formation of Cu-In-(Ga)-Se precursors and subsequent selenization to form CuIn(Ga)Se2. In this work, we have investigated and compared the possible interactions in Cu-In-Ga-Se systems, using sequentially stacked precursors premixed with Se, in order to get a better understanding of the Cu(In,Ga)Se2 thin film formation. Comparison of these SEM micrographs clearly revealed that the surface morphologies and hence surface roughness of the resulting Cu(In,Ga)Se2 absorber films were significantly influenced by the structure of the precursor films prior to selenization. XRD analyses revealed the presence of a graded CuIn1-xGaxSe structure, irrespective of the stacking order during the precursor formation step for samples selenized using elemental Se vapor. It was established that distinct from the case of using Se vapor, a single-phase Cu(In,Ga)Se2 films were obtained by diethylselenide (DESe) selenization from Cu-In-Ga metal precursors premixed Se irrespective of the stacking order during the precursor formation step. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Melt processed microporous films from compatibilized immiscible blends with potential as membranes

POLYMER ENGINEERING & SCIENCE, Issue 4 2002
M. Xanthos
Microporous flat films with potential as membranes were produced via melt processing and post-extrusion drawing from immiscible polypropylene/polystyrene blends containing a compatibilizing copolymer. The blends were first compounded in a co-rotating twin-screw extruder and subsequently extruded through a sheet die to obtain the precursor films. These were uniaxially drawn (100%,500%) with respect to the original dimensions to induce porosity and then post-treated at elevated temperatures to stabilize the resultant structure, which consisted of uniform microcracks in the order of a few nanometers in width. The effects of blend composition and extrusion process parameters on surface and cross-sectional porosity and solvent permeability of the prepared films are presented and related to specific microstructural features of the films before and after drawing. Finite element modeling of the stretching operation in the solid state yielded a successful interpretation of the blend response to uniaxial tension that resulted in microcrack formation. Comparison of some of the novel microporous structures of this work with commercial membranes prepared by solvent-based phase inversion processes suggests comparable pore size and porosity ranges, with narrower pore size distribution. [source]