Search results for "Fourier transform"
showing 10 items of 1138 documents
Near-field coupling of a point-like dipolar source with a thin metallic film: Implication for STM plasmon excitations
2012
International audience; Recent experiments have shown that it is possible to excite surface plasmons on metallic films by injecting tunnel electrons from a sharp metal tip located in the immediate proximity of the sample. When working close to a bare metal film, the excitation of surface plasmons gives rise to typical circular patterns that can be recorded in both image and Fourier planes. Important physical parameters of surface plasmon propagation such as their propagation length can be extracted from these images. In this Letter, we discuss theoretically the physics of the plasmonic excitations induced by a STM tip.
Effect of hydroxyapatite concentration and size on morpho-mechanical properties of PLA-based randomly oriented and aligned electrospun nanofibrous ma…
2019
The growing demand for nanofibrous biocomposites able to provide peculiar properties requires systematic investigations of processing-structure-property relationships. Understanding the morpho-mechanical properties of an electrospun scaffold as a function of the filler features and mat microstructure can aid in designing these systems. In this work, the reinforcing effect of micrometric and nanometric hydroxyapatite particles in polylactic acid-based electrospun scaffold presenting random and aligned fibers orientation, was evaluated. The particles incorporation was investigated trough Fourier transform infrared spectroscopy in attenuated total reflectance. The morphology of the nanofibers …
A simple interpretation of the effect of the polymer type on the properties of PMBs for road paving applications
2018
Abstract The paper presents the results of the rheological characterisation of polymer-modified bitumen for paving applications. In order to find a simple interpretation of the influence of polymer type on the blends produced, in this study high density and low density polyethylene (PE) with different chemical properties were used, as well as ethylene-vinyl acetate. The chemical characteristics of the base bitumen and the polymers used were determined by means of SARA analysis and Fourier Transform Infrared Spectroscopy, FTIR, respectively. The morphology of the produced blends was investigated by means of fluorescent light optic microscopy, while the mechanical properties were investigated…
Toward Photopatternable Thin Film Optical Sensors Utilizing Reactive Polyphenylacetylenes
2013
Substituted polyphenylacetylenes featuring reactive pentafluorophenyl (PFP) ester moieties are synthesized. Parts of the reactive PFP groups are then converted with a mono ortho-nitrobenzyl-protected diamine in variable ratios. Thin films are prepared from these copolymers and irradiated with UV light (λ = 365 nm), resulting in crosslinking of the irradiated areas and hence enabling a photopatterning. We found that during the photocrosslinking process, the excess of PFP ester moieties is stable and remained intact, enabling a subsequent post-polymerization modification step with amines. Noteworthy, this subsequent modification with amines results in a dramatically shift in the UV-vis absorp…
Investigation of Acetone Vapour Sensing Properties of a Ternary Composite of Doped Polyaniline, Reduced Graphene Oxide and Chitosan Using Surface Pla…
2020
This work reports the use of a ternary composite that integrates p-Toluene sulfonic acid doped polyaniline (PANI), chitosan, and reduced graphene oxide (RGO) as the active sensing layer of a surface plasmon resonance (SPR) sensor. The SPR sensor is intended for application in the non-invasive monitoring and screening of diabetes through the detection of low concentrations of acetone vapour of less than or equal to 5 ppm, which falls within the range of breath acetone concentration in diabetic patients. The ternary composite film was spin-coated on a 50-nm-thick gold layer at 6000 rpm for 30 s. The structure, morphology and chemical composition of the ternary composite samples were character…
E-beam irradiation and UV photocrosslinking of microemulsion-laden poly(N-vinyl-2-pyrrolidone) hydrogels for ‘‘in situ’’ encapsulation of volatile hy…
2011
Gelled microemulsions are the subject of considerable scientific and commercial interest. Many efforts are currently devoted to improving their toxicological profile and functioning as biocompatible diffusion barrier for the controlled delivery of hydrophobic compounds. In the present investigation, a non-ionic polymeric surfactant was chosen to generate an oil-in-water microemulsion of a model fragrance in the presence of poly(N-vinyl-2-pyrrolidone) (PVP). The microemulsion was then subjected to either electron-beam or UV-irradiation to induce free-radical crosslinking of PVP at low temperature and in the absence of crosslinking agents, catalysts and initiators. Irradiation conditions with…
Interpolymer complex between hydroxypropyl cellulose and maleic acid-styrene copolymer: phase behavior of semi-dilute solutions.
2005
Summary: The phase behavior of a water/hydroxypropyl cellulose/maleic acid–styrene copolymer (H2O/HPC/MAc-S) system was investigated in the semi-dilute range by turbidimetry, rheology, and optical microscopy. The two polymers under investigation form interpolymer complexes via hydrogen bonding. In the case of a total polymer concentration of cpol = 5 mg · mL−1 a second phase segregates upon heating the homogeneous ternary system. By applying a constant shear rate ( = 50 s−1) the phase separation temperature of the system is 10–15 °C lower than for an unsheared one. For cpol = 10 mg · mL−1 phase separation has already occurred at room temperature when the two binary polymer solutions are mix…
Direct synthesis of fibrous high molecular weight polyethylene using vanadium catalysts supported on an SiO2ionic liquid system
2015
Polyethylene of fibrous morphology was obtained using Cp2VCl2 and VCl2(salenCl2) catalysts activated by AlEt2Cl and AlEtCl2 and heterogenized on a supported ionic liquid system prepared with SiO2 and 1-(3-triethoxysilyl)propyl-3-methylimidazolium chloroaluminate. The fibre length ranges from 15 to 60 µm, depending on the reaction conditions. The polyethylene is characterized by a high molecular weight ((1.1–2.4) × 106 g mol−1) and a narrow molecular weight distribution (1.4–2.5). It is a linear polymer, properly without branching. The DSC method reveals characteristic changes in melting temperature and crystallinity degree between the first and second scan heating cycles (141 °C and 136 °C,…
Chemical characterization and ultrastructure study of pulp fibers
2020
Abstract Understanding the ultrastructure and chemical characterization of pulp fibers is highly important in utilizing wood as a raw material in a wide scope of applications, such as forest biomass-based biorefineries and low-cost renewable materials. The observation of the ultrastructure is not possible without advanced microscopy and spectroscopy techniques. Therefore, this study focuses on exploring the ultrastructure of pulp fibers with helium ion microscopy (HIM) and scanning electron microscopy (SEM). For the analysis of chemical characterization in the pulp fibers, Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS) were pe…
An Innovative Treatment Based on Sodium Citrate for Improving the Mechanical Performances of Flax Fiber Reinforced Composites
2021
The goal of this paper is to evaluate the effectiveness of a cost-effective and eco-friendly treatment based on the use of sodium citrate (Na3C6H5O7) on the mechanical properties of flax fiber reinforced composites. To this scope, flax fibers were soaked in mildly alkaline solutions of the sodium salt at different weight concentration (i.e., 5%, 10% and 20%) for 120 h at 25 °C. The modifications on fibers surface induced by the proposed treatment were evaluated through Fourier transform infrared analysis (FTIR), whereas scanning electron microscope (SEM) and helium pycnometer were used to obtain useful information about composites morphology. The effect of the concentration of the treating …