Search results for "Microscopy"
showing 10 items of 3390 documents
Splitting of Surface-Immobilized Multicompartment Micelles into Clusters upon Charge Inversion
2016
International audience; We investigate a morphological transition of surface-immobilized triblock terpolymer micelles: the splitting into well-defined clusters of satellite micelles upon pH changes. The multicompartment micelles are formed in aqueous solution of ABC triblock terpolymers consisting of a hydrophobic polybutadiene block, a weak polyanionic poly(methacrylic acid) block, and a weak polycationic poly(2-(dimethylamino)ethyl methacrylate) block. They are subsequently immobilized on silicon wafer surfaces by dip-coating. The splitting process is triggered by a pH change to strongly basic pH, which goes along with a charge reversal of the micelles. We find that the aggregation number…
Study of Morphology of Reactive Dissolution Interface Using Fractal Geometry
1996
J. Pharm. Sci. ISI Document Delivery No.: VF662 Times Cited: 7 Cited Reference Count: 15 Tromelin, A Gnanou, JC Andres, C Pourcelot, Y Chaillot, B; International audience; The determination of reactive fractal dimension was carried out using two forms of the Noyes-Whitney equation, -dQ/dt = K(Q/Q(0))(DR/3) and -d Q/dt = K' R(DR-3) using the Richardson plot on the basis of previous data obtained by dissolution of an orthoboric acid powder. The correlation of the results provided by the two ways of calculation allows proposal of the hypothesis that dissolution begins on a specific population of reactive sites and probably promotes the formation of microporous volumes or cracks.
PLA based biocomposites reinforced with Arundo donax fillers
2014
Abstract In this work, for the first time, a natural and almost inexpensive filler obtained by grinding the culms of Arundo donax was used to prepare PLA based biocomposites. The composites were prepared by melt compounding PLA with A. donax filler (ADF). The influence of the content and size of ADF on the morphology and on the mechanical and thermal properties of PLA–ADF composites was evaluated. Moreover, ADF was extracted from composites to evaluate the effect of processing on morphology and dimensions of the incorporated filler. Furthermore, the experimental elastic moduli of the biocomposites have been fitted, employing two theoretical models, i.e., Hill and Halpin–Tsai. The results sh…
Influence of short-term aging on mechanical properties and morphology of polymer-modified bitumen with recycled plastics from waste materials
2020
Polymer-modified bitumen (PMB) is bitumen that has been specifically engineered with polymer for providing enhanced performance in service. The aging of bitumen is a main aspect that is able to affect its final performance: during the production phase in a hot mix plant, all the binders experience short-term aging due to the high processing temperature. The same is true during the production of the modified binder, when the polymer is dispersed at high temperature in the bitumen mass. This paper aims at studying the effect of short-term aging when using different types of modifiers such as recycled polymers obtained from waste materials. A 50/70 penetration-grade bitumen has been modified, …
Structural Characterization of the “Knitting Pattern” in Polystyrene-block-poly(ethylene-co-butylene)-block-poly(methyl methacrylate) Triblock Copoly…
1998
In a polystyrene-block-polybutadiene-block-poly(methyl methacrylate) triblock copolymer (SBM) a morphological transition from a lamellar (ll) morphology (with sequence ABCB) to the knitting pattern (kp) morphology occurs upon hydrogenation of the center PB block. Structural information of the nonhydrogenated and the hydrogenated material is provided from small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). For the nonhydrogenated SBM sample the SAXS profile correlates well with a simple periodic lamellar structure. The hydrogenated sample forming the kp morphology displays a more complex SAXS pattern. From the TEM images of the knitting pattern the two-dimensional…
Growth and size distribution of Au nanoparticles in annealed Au/TiO2 thin films
2014
Abstract Nanocomposites consisting of noble metal nanoparticles (NPs) embedded in TiO2 thin films are of great interest for applications in optoelectronics, photocatalysis and solar-cells for which the plasmonic properties of the metal NPs play a major role. This work investigates the first stages of the formation of gold NPs by thermal annealing of Au-doped TiO2 thin films grown by magnetron sputtering. A low concentration of gold in the films is considered (5 at.%) in order to study the first stages of the formation of the NPs. Raman spectroscopy is used to follow the crystallization of TiO2 when increasing the annealing temperature. In addition, low-frequency Raman scattering (LFRS) is u…
Ceramic/metal nanocomposites by lyophilization: Processing and HRTEM study
2012
5 páginas, 8 figuras, 1 tabla.-- El pdf del artículo es el manuscrito de autor.
Incorporation of Mn12single molecule magnets into mesoporous silica
2003
The incorporation of four Mn12 derivatives, namely [Mn12O12(O2CR)16(H2O)4] (R = CH3 (1), CH3CH2 (2), C6H5 (3), C6F5 (4)), into the hexagonal channels of the MCM-41 mesoporous silica has been studied. Only the smallest clusters 1 and 2, i.e. those with compatible size with the pores of MCM-41, could enter into the mesoporous silica. Powder X-ray diffraction analysis, HRTEM images and N2 adsorption–desorption isotherm experiments show that the well-ordered hexagonal structure of MCM-41 is preserved and that the Mn12 clusters are inside the pores. The magnetic properties of the MCM-41/2b nanocomposite material obtained in CH2Cl2 indicate that the structure of the cluster is maintained after in…
Aggregation-induced heterogeneities in the emission of upconverting nanoparticles at the submicron scale unfolded by hyperspectral microscopy
2018
Transparent upconverting hybrid nanocomposites are exciting materials for advanced applications such as 3D displays, nanosensors, solar energy converters, and fluorescence biomarkers. This work presents a simple strategy to disperse upconverting b-NaYF4:Yb3+/Er3+ or Tm3+ nanoparticles into low cost, widely used and easy-to-process polydimethylsiloxane (PDMS)-based organic–inorganic hybrids. The upconverting hybrids were shaped as monoliths, films or powders displaying in the whole volume Tm3+ or Er3+ emissions (in the violet/blue and green/red spectral regions, respectively). For the first time, hyperspectral microscopy allows the identification at the submicron scale of differences in the …
Ceramic/metal nanocomposites by lyophilization: Spark plasma sintering and hardness
2014
The present study is focused on the procedure of spray-drying and lyophilization techniques for the preparation of ceramic/metal nanocomposites. The results of the study at all stages are compared with those corresponding to powders conventionally dried by heating in furnace. Starting from aqueous solutions of metal salts and ceramic powders, the procedure follows with spray-drying, lyophilization, calcination of the resulting powders and subsequent Spark Plasma Sintering (SPS). X-ray diffraction analysis of the powders at different stages of the processing routes was used for phase indexing; further characterization was performed by Transmission Electron Microscopy and Energy Dispersive X-…