Letteratura scientifica selezionata sul tema "Colloïde nanocomposite"
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Articoli di riviste sul tema "Colloïde nanocomposite"
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Park, Jong-Min, Chan-Woo Lee, Wan-Sul Lee, Kyung-Mo Yang, Jun-Ho Lee, Gi-Yong Nam, Seong-Hoon Lee, Yong Sang Lee, Youngkwan Lee e Jae-Do Nam. "MONTMORILLONITE-REINFORCED NATURAL RUBBER NANOCOMPOSITES THROUGH EMULSION STABILIZATION–DESTABILIZATION METHOD". Rubber Chemistry and Technology 85, n. 2 (1 giugno 2012): 165–79. http://dx.doi.org/10.5254/rct.12.88978.
Testo completoAbstract (sommario):
Abstract A nanoplatelet of montmorillonite (MMT) was incorporated in the natural rubber (NR) matrix at a high loading content using a newly developed stabilization–destabilization process in the colloid states. Examination of the surface charge of the colloid drops by zeta potential measurement led to the identification of the stable and unstable conditions of the colloid mixture as well as each colloid system as a function of pH. The stabilized mixture of the MMT and NR colloids was subsequently destabilized by changing the pH of the mixture to achieve a well-dispersed and intercalated NR/MMT precipitate. The resulting NR/MMT nanocomposites provided an exfoliated MMT morphology up to 25 phr, and the mechanical properties and aging tolerance of the resulting nanocomposite vulcanizates were substantially enhanced by the incorporated MMT nanofillers. The developed stabilization–destabilization methodology ensured a highly loaded MMT rubber composite system, which could be used to obtain high performance NR/MMT nanocomposite systems with ease without using high-shear processing techniques.
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Krkljes, Aleksandra, Miodrag Mitric e Zorica Kacarevic-Popovic. "Radiolytic synthesis and characterization of PVA/Au nanocomposites: The influence of pH values". Chemical Industry 62, n. 3 (2008): 101–6. http://dx.doi.org/10.2298/hemind0803101k.
Testo completoAbstract (sommario):
Nanocomposites which consist of polymer matrix and nanoparticles of noble metal are a very important class of nanomaterials. The optical properties of these materials are strongly dependent on the nanoparticles size as well as on the synthesized procedure of nanocomposites preparation. In this work the Au nanoparticles were synthesized by the simple radiolytic procedure, using steady state gamma irradiation, under different pH values. PVA/Au nanocomposite films were obtained by solvent evaporation from Au colloids. UV-Vis absorption spectra of Au colloids show absorption in the range of 450 to 650 nm with the maximum around 520 nm, which is the typical plasmon band of Au nanoparticles. Absorption spectra of PVA/Au nanocomposites are red shifted compared to corresponding primary Au colloids. This red shift is not result of any change in particle size distribution and can be explained by the change of dielectric property of surrounding medium. IR spectra indicated anchoring the OH groups of PVA molecule at the cluster surface. This effect limits the growing of the metal clusters and confirmed that the PVA is a god matrix for in situ synthesis of Au nanoparticles. The size of Au nanoparticles is dependent on the experimental conditions. Obtained results indicated that the pH value of solution played an important role. The values of absorption maximum (?max) were not dependent on the concentration of Au cations, but show strong dependence on the pH value of the initial solution. The increase of pH value reduced the mean diameters of nanoparticles. The lowest value of ?max was obtained for colloid with pH 7, which theoretically corresponds to the nanoparticles with minimum dimension. These results are in agreement with the XRD measurement of PVA/Au nanocomposite films and theoretical calculations. According to obtained results of radiolytic synthesis of Au nanoparticles in PVA solution can be conclude that it is possible to control the particle size by tuning the pH value of solution.
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Li, Bao Guang, Yong Zi Xu, Lu Bai, Huan Dai, Cai Cai Xie e Hai Bin Li. "Ultrasonic Effect on Fabrication of Intercalated MgAl-LDH/PVA Nanocomposites via Exfoliation-Adsorption Route". Key Engineering Materials 727 (gennaio 2017): 532–36. http://dx.doi.org/10.4028/www.scientific.net/kem.727.532.
Testo completoAbstract (sommario):
Glycine intercalated Mg/Al-layered double hydroxides (LDH-G)/PVA nanocomposites were prepared via exfoliation-adsorption route based on exfoliation of LDH-G in formamide. The effect of ultrasonic treatment on the fabrication of LDH-G/PVA nanocomposites was investigated. The results of XRD suggest that chains of PVA with double layer arrange into the galleries of restacking LDH platelets with the formation of intercalated-type nanocomposite. Experiments present that ultrasonic treatment on the colloid of LDH-G/PVA increases the amount of platelet which forms the intercalated phase, and improves the regularity of LDH-G arrays in the c direction. It is demonstrated the exfoliated LDH platelets orient in its normal paralleling the flow direction at the high shear rate induced by ultrasound. Simultaneously, under the enhanced temperature caused by long term of ultrasonic treatment, PVA chains extend more and the interaction between PVA chains and LDH layers is reinforced. A model was proposed for various stages of LDH platelets and PVA chains in their mixed colloid during ultrasonic treatment which describes the fabrication of improved hybrid structure.
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Susilowati, Endang, Mohammad Masykuri, Maria Ulfa e Dyah Puspitasari. "Preparation of Silver-Chitosan Nanocomposites Colloidal and Film as Antibacteri Material". JKPK (Jurnal Kimia dan Pendidikan Kimia) 5, n. 3 (31 dicembre 2020): 300. http://dx.doi.org/10.20961/jkpk.v5i3.46711.
Testo completoAbstract (sommario):
<p>Colloidal nanocomposites silver-chitosan have been made. Silver nanoparticles were produced by chemical reduction methods assisted microwave irradiation using chitosan from crab shells as a reducing agent and stabilizer, AgNO<sub>3 </sub>as a precursor and NaOH as an accelerator. This study investigated AgNO<sub>3</sub> concentration toward localized surface plasmon resonance (LSPR) phenomenon of nanocomposites colloidal. The size and shape of the silver nanoparticles were confirmed by TEM. Furthermore, the stability of the storage was observed for twelve weeks. Colloidal and film nanocomposites silver- chitosan have been made by casting method by drying at room temperature. After that, the film characterization was carried out, including swelling with gravimetry methods and surface morphology using scanning electron microscopy (SEM). Diffusion methods tested colloid antibacterial activity and silver-chitosan nanocomposite film’s against <em>E. Coli</em> and <em>S. Aureus</em>. The results showed that the formation of silver nanoparticles was identified by the LSPR absorption band's appearance at 413-419 nm. The increasing of AgNO<sub>3</sub> concentration increased the intensity of the LSPR absorption band. Silver nanoparticles with sizes of about 3-9 nm are spherical. The silver nanoparticles were stable at 12 weeks of storage. The higher AgNO<sub>3</sub> concentration tends to increase the swelling of the film. The surface of the silver-chitosan nanocomposite film’s was rougher than that of the chitosan film. The higher the silver nanoparticle concentration, the higher the colloid and film antibacterial activity against <em>E. Coli</em> and <em>S. Aureus.</em></p>
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Lozovski, V. Z., A. G. Vasiljev, T. A. Vasyliev, I. S. Petrik, A. M. Eremenko e N. P. Rybalchenko. "Resonance properties of the solution of quercetin stabilized silver nanoparticles in a nutrient medium". Himia, Fizika ta Tehnologia Poverhni 15, n. 1 (30 marzo 2024): 86–93. http://dx.doi.org/10.15407/hftp15.01.086.
Testo completoAbstract (sommario):
Changes in the light absorption spectrum when mixing colloids of Ag nanoparticles with a diameter of 7 nm in a quercetin shell with a nutrient medium were studied in the present article. Colloids of silver nanoparticles were prepared by chemical reduction of AgNO3 silver salt with sodium tetrahydroborate (NaBH4) in an aqueous solution. Quercetin is a flavonoid of plant origin. It was chosen to stabilize nanoparticles due to its capability to form complexes with metals. The quercetin shell is capable to preserve the bactericidal effect of silver NPs on bacteria and weaken their toxic effect on healthy cells of the human body. The absorption spectra of solutions from which nanoparticle colloids were synthesized were used to control the synthesis result. The Luria-Bertani nutrient medium was studied in the work. Absorption spectra of the nutrient medium and nanoparticle colloids were again obtained immediately before mixing. Then, the nutrient medium and the nanoparticle colloid were mixed in volume proportion 1:1, and the absorption spectrum of the mixture was mesured. The absorption spectrum of the mixture did not reproduce a simple overlay of the nanoparticle colloid spectrum on the absorption spectrum of the nutrient medium. To describe the experimental spectra, a colloid of stabilized silver nanoparticles, a nutrient medium, and a mixture of a colloid and a nutrient medium were considered by nanocomposites of various organic and inorganic nanoparticles in a liquid. As a result, experimental absorption spectra were theoretically approximated by related to these nanoparticles elementary oscillators. The error of the discrepancy between experimental and simulated spectra did not exceed 3%. Analysis of the complex spectra of the mixture of the nanoparticle colloid and the nutrient medium has shown that the frequency of the localized plasmon resonance in the nanoparticles most likely does not change. It means that for studying the effect of nanoparticles on biological objects (microbes or viruses), the wavelength of external irradiation must be chosen equal to the wavelength of LPR in the colloid.
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Velgosova, Oksana, Lívia Mačák, Erika Múdra, Marek Vojtko e Maksym Lisnichuk. "Preparation, Structure, and Properties of PVA–AgNPs Nanocomposites". Polymers 15, n. 2 (10 gennaio 2023): 379. http://dx.doi.org/10.3390/polym15020379.
Testo completoAbstract (sommario):
The aim of the work was to prepare a polymer matrix composite doped by silver nanoparticles and analyze the influence of silver nanoparticles (AgNPs) on polymers’ optical and toxic properties. Two different colloids of AgNPs were prepared by chemical reduction. The first colloid, a blue one, contains stable triangular nanoparticles (the mean size of the nanoparticles was ~75 nm). UV–vis spectrophotometry showed that the second colloid, a yellow colloid, was very unstable. Originally formed spherical particles (~11 nm in diameter) after 25 days changed into a mix of differently shaped nanoparticles (irregular, triangular, rod-like, spherical, decahedrons, etc.), and the dichroic effect was observed. Pre-prepared AgNPs were added into the PVA (poly(vinyl alcohol)) polymer matrix and PVA–AgNPs composites (poly(vinyl alcohol) doped by Ag nanoparticles) were prepared. PVA–AgNPs thin layers (by a spin-coating technique) and fibers (by electrospinning and dip-coating techniques) were prepared. TEM and SEM techniques were used to analyze the prepared composites. It was found that the addition of AgNPs caused a change in the optical and antibiofilm properties of the non-toxic and colorless polymer. The PVA–AgNPs composites not only showed a change in color but a dichroic effect was also observed on the thin layer, and a good antibiofilm effect was also observed.
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ALAM, FAHAD, SAJID ALI ANSARI, WASI KHAN, M. EHTISHAM KHAN e A. H. NAQVI. "SYNTHESIS, STRUCTURAL, OPTICAL AND ELECTRICAL PROPERTIES OF IN-SITU SYNTHESIZED POLYANILINE/SILVER NANOCOMPOSITES". Functional Materials Letters 05, n. 03 (settembre 2012): 1250026. http://dx.doi.org/10.1142/s1793604712500269.
Testo completoAbstract (sommario):
Polyaniline (PANI) is recognized as one of the most important conducting polymers due to its high conductivity and good stability. In this paper, polyaniline/silver (PANI/Ag) nanocomposites were synthesized by in-situ polymerization of aniline using ammonium peroxydisulphate (APS) as oxidizing agent with varying concentration of Ag nanoparticles colloids (0 ml, 25 ml and 50 ml). Silver nanoparticles were synthesized separately in colloidal form from silver nitrate (Ag2NO3) with the help of reducing agent sodium borohydride (NaBH4). The PANI/ Ag nanocomposites were characterized by XRD, SEM, AFM, UV-visible, temperature dependent resistivity and dielectric measurements. All samples show a single phase nature of the nanoparticles. The electrical resistivity as function of temperature was measured in the temperature range 298–383 K, which indicates a semiconducting to metallic transition at 373 K and 368 K for 25 ml and 50 ml silver colloid samples, respectively.
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LEPESHKIN, N. N., W. KIM, V. P. SAFONOV, J. G. ZHU, R. L. ARMSTRONG, C. W. WHITE, R. A. ZUHR e V. M. SHALAEV. "OPTICAL NONLINEARITIES OF METAL-DIELECTRIC COMPOSITES". Journal of Nonlinear Optical Physics & Materials 08, n. 02 (giugno 1999): 191–210. http://dx.doi.org/10.1142/s021886359900014x.
Testo completoAbstract (sommario):
Nonlinear optical properties of metal-dielectric composites, such as fractal colloid aggregates and clusters created by ion implantation, are studied. Strong fluctuations of local fields result in huge enhancements of optical nonlinearities in fractal colloid aggregates. The real and imaginary parts of the cubic susceptibility of silver colloid aggregates are measured. It is found that the coefficient of nonlinear absorption strongly depends on the laser wavelength and intensity. Optical limiting effect in fractal silver colloids is observed. Nondegenerate forward four-wave mixing technique is used to investigate the third-order nonlinear susceptibility for nanocomposite material with Au nanocrystals formed inside a SiO 2 glass matrix. The Au nanocrystals are formed by the ion implantation and annealing method that produces very high volume fraction of nanoparticles. The large value |χ(3)|=1.3×10-7 esu is measured. Two characteristic relaxation times, 5.3 ps and 0.66 ps, are estimated from the detuning curve of |χ(3)|, as the probe beam wavelength changes. A novel class of optical materials, microcavities doped with nanostructured fractal aggregates, is also studied. In our experiments, lasing at extremely low pump intensities, below 1 mW, and dramatically enhanced Raman scattering was observed in microcavity/fractal composites.
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Irimpan, Litty, V. P. N. Nampoori e P. Radhakrishnan. "Enhanced luminescence and nonlinear optical properties of nanocomposites of ZnO–Cu". Journal of Materials Research 23, n. 11 (novembre 2008): 2836–45. http://dx.doi.org/10.1557/jmr.2008.0364.
Testo completoAbstract (sommario):
In this article, we present the spectral and nonlinear optical properties of ZnO–Cu nanocomposites prepared by colloidal chemical synthesis. The emission consisted of two peaks. The 385-nm ultraviolet (UV) peak is attributed to ZnO and the 550-nm visible peak is attributed to Cu nanocolloids. Obvious enhancement of UV and visible emission of the samples is observed and the strongest UV emission of a typical ZnO–Cu nanocomposite is over three times stronger than that of pure ZnO. Cu acts as a sensitizer and the enhancement of UV emission are caused by excitons formed at the interface between Cu and ZnO. As the volume fraction of Cu increases beyond a particular value, the intensity of the UV peak decreases while the intensity of the visible peak increases, and the strongest visible emission of a typical ZnO–Cu nanocomposite is over ten times stronger than that of pure Cu. The emission mechanism is discussed. Nonlinear optical response of these samples is studied using nanosecond laser pulses from a tunable laser in the wavelength range of 450–650 nm, which includes the surface plasmon absorption (SPA) band. The nonlinear response is wavelength dependent and switching from reverse saturable absorption (RSA) to saturable absorption (SA) has been observed for Cu nanocolloids as the excitation wavelength changes from the low absorption window region to higher absorption regime near the SPA band. However, ZnO colloids and ZnO–Cu nanocomposites exhibit induced absorption at this wavelength. Such a changeover in the sign of the nonlinearity of ZnO–Cu nanocomposites, with respect to Cu nanocolloids, is related to the interplay of plasmon band bleach and optical limiting mechanisms. The SA again changes back to RSA when we move over to the infrared region. The ZnO–Cu nanocomposites show self-defocusing nonlinearity and good nonlinear absorption behavior. The nonlinear refractive index and the nonlinear absorption increases with increasing Cu volume fraction at 532 nm. The observed nonlinear absorption is explained through two-photon absorption followed by weak free-carrier absorption and interband absorption mechanisms. This study is important in identifying the spectral range and composition over which the nonlinear material acts as a RSA-based optical limiter. ZnO–Cu is a potential nanocomposite material for the light emission and for the development of nonlinear optical devices with a relatively small limiting threshold.
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Boissière, Michel, Joachim Allouche, Roberta Brayner, Corinne Chanéac, Jacques Livage e Thibaud Coradin. "Design of Iron Oxide/Silica/Alginate HYbrid MAgnetic Carriers (HYMAC)". Journal of Nanoscience and Nanotechnology 7, n. 12 (1 dicembre 2007): 4649–54. http://dx.doi.org/10.1166/jnn.2007.18118.
Testo completoAbstract (sommario):
A large number of natural and synthetic polymers have already been evaluated for the design of nanomaterials incorporating magnetic nanoparticles for biomedical applications. The possibility to use hybrid (bio)-organic/inorganic nano-carriers have been much less studied. Here we describe the design of Hybrid MAgnetic Carriers (HYMAC) consisting of alginate/silica nanocomposites incorporating magnetite nanoparticles, based on a spray-drying approach. Transmission electron microscopy and X-ray energy dispersive spectrometry confirm the successful incorporation of magnetic colloids within homogeneous hybrid capsules. X-ray diffraction data suggest that surface iron ions are partially desorbed by the spray-drying process, leading to the formation of lepidocrocite and of an iron silicate phase. Magnetic measurements show that the resulting nanocomposites exhibit a superparamagnetic behaviour with a blocking temperature close to 225 K. Comparison with un-silicified capsules indicate that the mineral phase enhances the thermal stability of the polymer network and do not modify of the amount of incorporated iron oxide nanoparticles. Moreover, evaluation of nanocomposite up-take by fibroblasts indicates their possible internalization. A selective intracellular alginate degradation is observed, suggesting that these HYMAC nanomaterials may exhibit interesting properties for the design of drug delivery devices.
Tesi sul tema "Colloïde nanocomposite"
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Ma, Huanhuan. "Synthesis of silica/polymer hybrid particles with controlled morphologies through polymerization induced co-assembly of grafted and free block copolymers". Electronic Thesis or Diss., Lyon 1, 2024. http://www.theses.fr/2024LYO10330.
Testo completoAbstract (sommario):
Les colloïdes nanocomposites organiques/inorganiques suscitent une attention considérable en raison de leur large gamme d'applications potentielles. L'auto-assemblage induit par la polymérisation (PISA) de copolymères à blocs en surface de nanoparticules inorganiques est reconnu comme une stratégie particulièrement efficace pour la synthèse de ces matériaux. Cette étude vise à synthétiser des brosses de polymères hydrophiles à la surface de particules de silice en utilisant la polymérisation radicalaire contrôlée par la voie nitroxyde (NMP) et à les utiliser par la suite comme macroamorceurs pour la croissance d'un second bloc hydrophobe. Des colloïdes hybrides avec des morphologies bien définies sont ainsi obtenus grâce à l'auto-assemblage des copolymères à blocs greffés et de leurs analogues non greffés. La première partie de ce travail est dédiée au greffage de brosses de polyélectrolytes faibles, le poly(acide méthacrylique-co-styrène) (P(AMA-co-S)), à partir de la surface de particules de silice. Des alcoxyamines ont été liées de manière covalente à des particules de silice de tailles variées en deux étapes, et avec une large gamme de densités de greffage. Ces particules de silice modifiées ont ensuite été utilisées comme amorceurs « supportés » pour la NMP de l’acide méthacrylique (AMA) en présence d’une faible quantité de styrène. En faisant varier systématiquement les conditions expérimentales, des particules de silice fonctionnalisées par des brosses de P(AMA-co-S) présentant différentes densités de greffage et différentes masses molaires, ont été obtenues. Leur comportement en solution aqueuse en fonction du pH et de la présence de sel ajouté a ensuite été étudié. Les particules de silice fonctionnalisées par les chaînes de P(AMA-co-S) ont été ensuite utilisées pour amorcer la copolymérisation en émulsion du méthacrylate de méthyle (MMA) et du styrène en présence de macroamorceur non greffé. Les expériences de contrôle effectuées en l’absence de silice ont conduit à la formation de particules de latex sphériques auto-stabilisées par le procédé PISA. L’influence de la concentration en macroamorceur, de sa masse molaire, du taux de solide et de la température sur la cinétique de polymérisation et la taille des particules de latex a été étudié en détails. Lorsque les particules de silice greffées ont été utilisées, l'auto-assemblage des copolymères à blocs amphiphiles à leur surface a conduit à la formation de particules hybrides de type framboise, cœur-coquille ou multicœur, en fonction de la taille des particules de silice, de la concentration en sel, ainsi que de la densité de greffage ou de la masse molaire du macroamorceur utilisé. La troisième partie de ce travail est consacrée à la synthèse par NMP de nano-objets à base de copolymères à blocs de type P(AMA-co-S)-b-P(MABz-co-S) stabilisés stériquement, par polymérisation en dispersion du méthacrylate de benzyle (MABz) en milieu alcoolique. La polymérisation réalisée à 85°C dans l'éthanol absolu est bien contrôlée, et conduit à la formation de particules sphériques, ainsi qu’à des morphologies supérieures telles que des batônnets, des fibres ou des vésicules selon la masse molaire du macroamorceur, de sa concentration et de la teneur en monomère. En présence des particules de silice fonctionnalisées, des morphologies hybrides originales composées de fibres courtes ou de vésicules liées à la surface de la silice ont été obtenues à nouveau par co-assemblage entre les chaînes de copolymères à bloc greffées et les chaînes non greffées. Ainsi, en faisant varier les conditions expérimentales et la nature chimique du monomère hydrophobe, une large gamme de morphologies hybrides a été obtenue à partir des mêmes particules de silice modifiées par des brosses de PAMAOrganic/inorganic nanocomposite colloids are attracting considerable attention due to their diverse range of potential applications. Polymerization-induced self-assembly of block copolymers on the surface of inorganic nanoparticles is recognized as a particularly effective strategy for the synthesis of these materials. This study aims to synthesize hydrophilic polymer brushes on silica particles using nitroxide-mediated radical polymerization (NMP) and subsequently employ them as macroinitiators for the growth of a second hydrophobic block. Hybrid colloids with well-defined morphologies are thus obtained through the co-assembly of surface-grafted and “free” ungrafted block copolymers. The first part of this work explores the grafting of weak polyelectrolyte brushes, namely poly(methacrylic acid-co-styrene) (P(MAA-co-S)), from the surface of silica particles. Alkoxyamine initiators were covalently attached to silica particles of varying sizes in two-steps, resulting in a large range of alkoxyamine grafting densities. These modified silica particles were subsequently employed as initiators for the NMP of MAA in the presence of a small amount of styrene as a controlling comonomer. By systematically varying the experimental conditions, silica particles functionalized with P(MAA-co-S) brushes, with tunable grafting densities and molar masses, were synthesized, and their pH- and salt-responsive behaviors were investigated. The resulting P(MAA-co-S)-functionalized silica particles were then employed in the aqueous emulsion copolymerization of methyl methacrylate (MMA) and styrene in the presence of free macroinitiator. Control experiments conducted without silica produced electrosterically stabilized spherical latex particles via polymerization-induced self-assembly. The effects of macroinitiator concentration, molar mass, solids content, and temperature on the polymerization kinetics and latex particles size were systematically studied. When PMAA-grafted silica particles were used, the co-assembly of the amphiphilic block copolymers on the silica surface and in solution, resulted in hybrid particles with raspberry, core-shell, or multicore morphologies depending on silica particle size, salt concentration, and the grafting density and molecular weight of the macroinitiator. The third part of this work reports the synthesis of sterically stabilized P(MAA-co-S)-b-P(BzMA-co-S) block copolymers nano-objects through alcoholic NMP dispersion polymerization of benzyl methacrylate (BzMA). The polymerization was well-controlled at 85°C in pure ethanol, producing copolymers that not only formed spherical particles but also self-assembled into more complex structures, such as worms and vesicles depending on the molar mass or concentration of the macroinitiator, and monomer content. Upon introducing P(MAA-co-S)-functionalized silica particles into the dispersion polymerization system, co-assembly of grafted and free block copolymers resulted in original hybrid morphologies composed of surface-tethered short worms or vesicles. By modifying the reaction conditions and monomer types, a wide range of nanocomposite colloidal morphologies were achieved using the same polymer brush-modified silica particles
2
Sun, Yangyang. "Study on the Nanocomposite Underfill for Flip-Chip Application". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/13975.
Testo completoAbstract (sommario):
Underfill material is a special colloidal dispersion system with silicon dioxide particles in the organic liquid. It is used to improve the reliability of integrated circuits (IC) packaging in the microelectronics. In order to successfully synthesize the nanocomposite underfill meeting the requirements of the chip package, it is necessary to have a fundamental understanding about the particle stability in the non-aqueous liquid and the relationship between materials properties and interphase structure in the composite. The results of this thesis contribute to the knowledge of colloidal dispersion of nanoparticles in organic liquid by systematically investigating the effects of particle size, particle surface chemistry and surface tension, and liquid medium polarity upon the rheological and thermal mechanical properties of underfill materials. The relaxation and dielectric properties studies indicate that the polymer molecular chain motion and polarization in the interphase region can strongly influence the material properties of nanocomposite, and so a good interaction between particle and polymer matrix is key. With this study, a potential nanocomposite underfill can be synthesized with low viscosity, low thermal expansion, and high glass transition temperature. The excellent transmittance of nanoparticles leads to further investigation of their ability as reinforcing filler in the photo-curable polymer.
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Klein, Guillaume. "Propriétés tribologiques de films issus de latex acryliques nanocomposites". Strasbourg, 2010. http://www.theses.fr/2011STRA6067.
Testo completoAbstract (sommario):
Parmi les applications des colloïdes polymères aqueux, le domaine des revêtements est prédominant. Dans cette spécialité, la compréhension des propriétés mécaniques, en particulier tribologiques, est essentielle. La problématique générale de cette thèse s’inscrit dans l’amélioration de la compréhension du comportement tribologique de films issus de latex soumis au frottement d’une bille d’acier. Deux types de systèmes de latex acryliques bien distincts se dégagent de cette thèse. D’une part des systèmes modèles, où nous avons fait varier certaines grandeurs physico-chimiques pertinentes, susceptibles d’influencer la morpholgie particulière des films (composition, pH, quantité de tensioactif post-ajoutée) et d’autre part, des systèmes nanocomposites où une hétérogénéité de structure a été introduite (argile ou oxyde de cérium). Des essais ont été réalisés sur couches minces à l’aide d’un tribomètre équipé d’une caméra permettant de visualiser in-situ la géométrie du contact du frotteur sphérique sur les films de latex transparents. Il a été montré que la transition vitreuse est clairement visible par un pic de frottement après obtention de courbes maîtresses. La position de ce pic de dissipation a été comparée au pic de facteur de perte, obtenues via des essais volumiques, ce qui amène à de discuter de la pertinence de longueur caractéristique de vitesse de déformation en frottement. D’un point de vue physico-chimique, la formation et la structuration des films peuvent être directement corrélées aux propriétés tribologiques. Des effets de composition, pH, migration de tensioactifs et de microstructuration ont été mis en évidenceAmong the applications of colloidal aqueous polymers, coatings are predominant. In this specialty, an understanding of mechanical properties, especially tribological, is essential. The general problematic of this thesis is to improve the understanding of the tribological behavior of films from latex subjected to the friction of a steel bead. Two types of distinct acrylic latex systems emerge from this thesis. Firstly, model systems, where we varied some relevant physical-chemical parameters that may influence particular latex film morphology (composition, pH, amount of surfactant post-added) and on the other hand, nanocomposites systems where a structure heterogeneity was introduced (clay or cerium oxide). Tests were performed on thin film using a tribometer equipped with a camera to visualize the in situ geometry of the contact area on the transparent latex films. It was shown that the glass transition is clearly visible by a friction peak after obtaining master curves. The position of this peak of dissipation was compared to the peak of loss factor, obtained through dynamic mechanical thermal analysis, which leads to discuss the relevance of the characteristic length of strain rate in friction. From a physico-chemical point of view, latex synthesis, post-synthesis parameter and structure of films can be directly correlated to tribological properties
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Kostadinova, Dessislava. "Préparation et caractérisation de catalyseurs métaux supportés à partir de nanocomposites colloïdes métalliques/HDL". Montpellier 2, 2007. http://www.theses.fr/2007MON20211.
Testo completo
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Sun, Zhengfei Wei Yen. "Novel sol-gel nanoporous materials, nanocomposites and their applications in bioscience /". Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/556.
Testo completo
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Oberdisse, Julian. "STRUCTURES DANS LES COLLOÏDES ET NANOCOMPOSITES DESTINES AU RENFORCEMENT : ETUDE PAR DIFFUSION DE NEUTRONS AUX PETITS ANGLES". Habilitation à diriger des recherches, Université Montpellier II - Sciences et Techniques du Languedoc, 2005. http://tel.archives-ouvertes.fr/tel-00010688.
Testo completoAbstract (sommario):
Dans la première partie, nous présentons l'étude de la structure de nanocomposites nanosilice-latex et de colloïdes (micelles adsorbées, complexes de colloïdes), par diffusion de neutrons aux petits angles. Dans la deuxième partie, les propriétés mécaniques des nanocomposites sont discutées. Nous présentons également une simulation numérique d'un réseau de polymères très enchevetré. Dans le dernier chapitre, nous décrivant un prototype de spectromètre de diffusion de neutrons aux très petits angles, installé au Laboratoire Léon Brillouin.
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Brunet, Paul. "Procédé de dépôt de couches minces nanocomposites par décharge à barrière diélectrique : de l'aérosol d'une suspension colloïdale à la morphologie du dépôt". Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0018.
Testo completoAbstract (sommario):
Le développement de procédé évoluant à la pression atmosphérique représente un enjeu majeur dans le dépôt de couches minces nanocomposites. Parmi ces procédés, les Décharges à Barrières Diélectriques présentent l'avantage d'être un procédé vert sans effluent gazeux, pouvant facilement être intégrées dans une chaine de production industrielle. L'approche choisie pour la réalisation de couches minces nanocomposites repose sur l'injection sous forme d'aérosol d'une suspension colloïdale dans la DBD. Les nanoparticules semi-conductrices de TiO2 sont choisies et mise en suspension dans un alcool polymérisable tel que l'isopropanol. L’objectif de ce travail est de contrôler le transport des nanoparticules et la croissance de la matrice dans la DBD en vue de réaliser une couche mince nanocomposite.Différentes méthodes de formation de l'aérosol et de filtration sont évaluées, ainsi que différents gaz vecteur (Ar, N2). Dans tous les cas considérés, la décharge est filamentaire.L'estimation des valeurs des différentes forces s'exerçant sur une nanoparticule dans une DBD confortée par un modèle numérique à permis d'orienter les expérimentations. Il est ainsi possible, à partir des paramètres permettant de générer le plasma, d'influencer le dépôt des nanoparticules et la croissance de la matrice. Les dépôts obtenus sont analysés ex situ par microscopie électronique à balayage, spectroscopie infrarouge, Raman et à rayon X et in situ avec la diffusion laser.Dans le régime filamentaire considéré, nous montrons que le flux de gaz et la fréquence de la tension joue des rôles prépondérants sur le dépôt des couches minces nanocomposites. Cette étude a permis de mettre en évidence qu’une simple fréquence n’est pas suffisante pour déposer la couche mince nanocomposite. Cependant l’utilisation d’une double fréquence semble être la meilleure approche pour séparer le transport des nanoparticules de celui de la croissance de la matriceDevelopment of an atmospheric pressure process presents a major concern in the deposition of nanocomposites thin films. Among these processes, Dielectrics Barrier Discharges takes advantages to be green processes without gas effluent, which can be easily integrate in an industrial line production. The chosen approach for the nanocomposite thin film deposition is based on the injection of an aerosol of a colloidal suspension in the DBD. Semi-conductive TiO2 nanoparticles are chosen and put in suspension in a polymerizable alcohol as isopropanol. The objective of the present work is to control the transport of the nanoparticles as well as the matrix growth in the DBD in order to realize the nanocomposites thin film Different methods of the aerosol formation and filtration are evaluated, as well as the carrier gas (Ar, N2). In each case considered, the discharge works in filamentary. Estimating values of the different forces acting on the nanoparticles in a DBD comforted by a numerical model allowed to guide the experimentations. Thanks to the parameter which generated the plasma, it is possible to influence the nanoparticles deposition and the matrix growth. Depositions are ex situ analyzed by scanning electron microscopy, Infra-red, Raman, and X-ray spectroscopy and in situ by laser scattering. In the filamentary regime considered, we show that the gas flow rate and the frequency of the voltage play a dominant role on the deposition of nanocomposites thin films. This study allowed to highlight that a simple frequency is not enough to deposit the nanocomposite thin film. However, the use of a double frequencies seems to be the best way to separate the nanoparticles transport to the surface from that of the matrix growth
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Goetz, Lee Ann. "Preparation and analysis of crosslinked lignocellulosic fibers and cellulose nanowhiskers with poly(methyl-vinyl ether co maleic acid) â " polyethylene glycol to create novel water absorbing materials". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45893.
Testo completoAbstract (sommario):
The search for cellulosic based products as a viable alternative for petroleum-based products was the impetus for covalently crosslinking lignocellulosic fibers and nanocellulose whiskers with poly(methyl vinyl ether) co maleic acid (PMVEMA) - polyethylene glycol (PEG). The lignocellulosics used were ECF bleached softwood (pine) and ECF bleached birch kraft pulp. This thesis also tests the hypothesis that water absorption and retention can be improved by grafting PMVEMA-PEG to the surface of ECF bleached kraft pulp hardwood and softwood fibers via microwave initiated crosslinking. The crosslinking of the PMVEMA to hardwood and softwood kraft ECF bleached pulp fibers resulted in enhanced water absorbing pulp fibers where the PMVEMA is grafted onto the surface of the fibers. The crosslinking was initiated both thermally and via microwave irradiation and the water absorption and water retention was measured as the percent of grafted PMVEMA. This was the first application of microwave crosslinking of pulp fibers with the goal of creating water absorbing pulp fibers. Ultimately, the water absorption values ranged from 28.70 g water per g dry crosslinked pulp fiber (g/g) to 230.10 g/g and the water retention values ranged from 26% to 71% of the water retained that was absorbed by the crosslinked pulp fibers. The microwave initiated crosslinked fibers had comparable results to the thermally crosslinked fibers with a decreased reaction time, from 6.50 min (thermal) to 1 min 45 sec (microwave).
Cellulose nanowhiskers, crystalline rods of cellulose, have been investigated due to their unique properties, such as nanoscale dimensions, low density, high surface area, mechanical strength, and surface morphology and available surface chemistry. Prior to this study, the crosslinking of cellulose whiskers with the matrix via solution casting of liquid suspensions of whiskers and matrix had not been explored. The hypothesis to be investigated was that incorporating cellulosic whiskers with the PMVEMA-PEG matrix and crosslinking the whiskers with the matrix would yield films that demonstrate unique properties when compared to prior work of crosslinking of PMVEMA-PEG to macroscopic ECF bleached kraft pulp fibers.
Solution cast composites of cellulose nanowhiskers-PMVEMA-PEG were crosslinked at 135 °C for 6.5 min and analyzed for crosslinking, thermal stability, strength and mechanical properties, whisker dispersion, and water absorption and uptake rates. The whisker-composites demonstrated unique properties upon crosslinking the whiskers with PMVEMA-PEG, especially the elongation at break and tensile strength upon conditioning of the final materials at various relative humidities. In addition, the whiskers improved the thermal stability of the PMVEMA-PEG matrix. This is significant as methods of improving processing thermal stability are key to developing new materials that utilize cellulose whiskers, PMVEMA, and PEG. This thesis addresses the hypothesis that cellulose nanowhiskers that are crosslinked with a matrix can create new whisker-matrix composites that behave differently after crosslinking.
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Wang, Sheng. "Phosphorus-Containing Polymers, Their Blends, and Hybrid Nanocomposites with Poly(Hydroxy Ether), Metal Chlorides, and Silica Colloids". Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/26789.
Testo completoAbstract (sommario):
Phosphorus-containing high performance polymers have been extensively studied during the last 10 years. These materials are of interest for a variety of optical and fire resistant properties, as well as for their ability to complex with the inorganic salts. This dissertation has focused on the nature of the phosphonyl group interactions with hydroxyl containing polymers, such as the poly(hydroxy ether)s. These may be considered linear models of epoxy resins and are also closely related to dimethacrylate (vinyl ester) matrix resins that are important for composite systems. It has been shown that bisphenol A poly(arylene ether phosphine oxide/sulfone) homo- or statistical copolymers are miscible with a bisphenol A-epichlorohydrin based poly(hydroxy ethers) (PHE), as shown by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC), infrared spectroscopy and , solid state cross polarization-magic angle spinning nuclear magnetic resonance (CP-MAS). These measurements illustrate the strong hydrogen bonding between the phosphonyl groups of the copolymers and the pendent hydroxyl groups of the PHE as the miscibility inducing mechanism. Complete miscibility at all blend compositions was achieved with as little as 20 mole% of phosphine oxide units in the poly(arylene ether) copolymer. Replacement of the bisphenol A moiety by other diphenols, such as hydroquinone, hexafluorobisphenol A and biphenol did not significantly affect blend miscibilities. Miscible polymer blends with PHE were also made by blending poly(arylene thioether phosphine oxide), and fully cyclized phosphine oxide containing polyimides based on (prepared from 2,2'-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and bis(m-aminophenyl) methyl phosphine oxide (DAMPO)) or bis(m-aminophenyl) phenyl phosphine oxide).
Additional research has focused on the influence of these materials on the property characteristics of vinyl ester matrix resins and has shown that the concentration of phosphonyl groups controls the homogeneity of both oligomers and the resulting networks. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fracture toughness measurements further confirmed the qualitative observations.
Metal salts, such as CoCl2 and CuCl2 had earlier been demonstrated to form complexes/nanocomposites with phosphorus-containing poly(arylene ethers). It has been possible to prepare transparent films with 100 mol% of metal chlorides, based upon the phosphonyl groups. The films are transparent, unlike the opaque polysulfone control systems. FTIR results suggested the formation of inorganic salt and polymer complexes at low concentrations. TEM showed homogeneous morphology at low concentrations and excellent dispersion even at high mole % of salts. Cobalt materials reinforce the basic poly(arylene ether)s to provide higher modulus values and influence positively the char yield generated after TGA experiments in air. The cobalt salt/BPADA-DAMPO polyimide composites also yield transparent films, implying very small dimensions.
Silica-polymer nanocomposites were also produced by mixing commercial silica colloid/N,N-dimethylacetamide (DMAc) fine dispersions (~ 12 nm) with bisphenol A poly(arylene ether phenyl phosphine oxide). The dry films produced by solution casting are transparent and silica colloids are evenly dispersed (~ 12 nm) into the polymer matrix as shown by TEM. These nanocomposites increased char yield compared with the polymer control, suggesting their fire retardant character. In comparison, the silica/polysulfone hybrid films prepared by the same methods were opaque and the char yield was not improved. This different phase behavior has been explained to be due to the hydrogen bonding between phosphonyl groups and silanol hydroxyl groups on the surface of the nanosilica.Ph. D.
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Profili, Jacopo. "Dépôt de couches minces nanocomposites par nébulisation d'une suspension colloïdale dans une décharge de Townsend à la pression atmosphérique". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30131/document.
Testo completoAbstract (sommario):
Ce travail de thèse porte sur le développement de nouvelles couches minces nanocomposites par plasma froid à la pression atmosphérique. L'objectif principal est d'améliorer la compréhension des mécanismes physico-chimiques régissant ce procédé de synthèse. La stratégie adoptée est basée sur l'injection via un aérosol d'une suspension colloïdale de nanoparticules d'oxyde métallique dans une décharge à barrière diélectrique opérant en atmosphère d'azote (décharge de Townsend). Dans un premier temps, la synthèse est réalisée de manière séquentielle, la fabrication d'une matrice inorganique de silice (SiO2) étant séparée du dépôt des nanoparticules (TiO2). Ensuite, les couches nanocomposites sont obtenues par un procédé en une seule étape à travers l'injection simultanée dans la décharge des nanoparticules et d'un précurseur polymérisable organosiliciée (HMDSO). Les travaux présentés dans ce manuscrit se divisent en quatre grandes parties : tout d'abord le procédé de fabrication des nanoparticules est présenté, et une étude de leur dispersion dans divers solvants chimiques est réalisée. Puis la deuxième partie s'intéresse à l'étape de nébulisation de la suspension colloïdale, à l'analyse des distributions de taille des objets injectés et à l'étude de leur transport sans plasma. En particulier, une étude de l'influence des principales forces agissant sur leur transport est réalisée. Ces résultats permettent ensuite d'évaluer l'impact de la décharge sur le transport, et sur la réalisation des couches minces nanocomposites. Finalement, l'analyse des propriétés obtenues pour ces couches minces sur des substrats de bois est présentée dans une dernière partieThis PhD work is focused on the development of a new generation of nanocomposite thin films using cold plasma at atmospheric pressure. The main objective is to improve the understanding of the mechanisms involved in this process.The strategy is based on the injection of a metal oxide nanoparticles suspension in a dielectric barrier discharge operating in nitrogen (Townsend discharge). At first, the nanocomposite thin film is deposited sequentially: the fabrication of the inorganic matrix of silica (SiO2) is separated from the collection of the nanoparticles (TiO2). Then, the nanocomposite layers are obtained by a one-step process using a direct injection inside the discharge of nanoparticles dispersed in a polymerizable organosilicon precursor (HMDSO). This manuscript is divided into four major parts: first, the synthesis of the nanoparticles and the study of their dispersion in different solvents are presented. Then, in the second part we focus on the atomization of the colloidal suspension, on the analysis of the size distributions of the injected objects and on the study of their transport towards the discharge area. These results are then used to assess the influence of the discharge on the transport and the quality of deposited nanocomposite thin films. Finally, the thin films properties are investigated when depositing on wood substrates
Libri sul tema "Colloïde nanocomposite"
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Bouzid, Menaa, a cura di. Bioencapsulation in silica-based nanoporous sol-gel glasses. Hauppauge, N.Y: Nova Science Publishers, 2009.
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Lee, B., N. A. Peppas, J. Kim, J. Y. Chang, D. Y. Godovsky, M. J. Han, C. M. Hassan, Y. Lee, R. P. Quirk e T. Yoo. Biopolymers - Pva Hydrogels Anionic Polymerisation Nanocomposites. Springer, 2013.
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(Contributor), J. Y. Chang, D. Y. Godovsky (Contributor), M. J. Han (Contributor), C. M. Hassan (Contributor), J. Kim (Contributor), B. Lee (Contributor), Y. Lee (Contributor), N. A. Peppas (Contributor), R. P. Quirk (Contributor) e T. Yoo (Contributor), a cura di. Biopolymers/PVA Hydrogels/Anionic Polymerisation/ Nanocomposites (Advances in Polymer Science). Springer, 2000.
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Kickelbick, Guido, Massimo Guglielmi e Alessandro Martucci. Sol-Gel Nanocomposites. Springer, 2014.
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Kickelbick, Guido, Massimo Guglielmi e Alessandro Martucci. Sol-Gel Nanocomposites. Springer, 2016.
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Capek, Ignac. Nanocomposite structures and dispersions, Volume 23 (Studies in Interface Science). Elsevier Science, 2006.
Cerca il testo completoCapitoli di libri sul tema "Colloïde nanocomposite"
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Mittal, Vikas. "Characterization of Polymer Nanocomposite Colloids by Sedimentation Analysis". In Characterization Techniques for Polymer Nanocomposites, 303–21. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2012. http://dx.doi.org/10.1002/9783527654505.ch12.
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Oliveira, M. M., D. Zanchet, D. Ugarte e A. J. G. Zarbin. "Synthesis and characterization of silver nanoparticle/polyaniline nanocomposites". In Surface and Colloid Science, 126–30. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/b97108.
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Oberdisse, J., e F. Boué. "Rheology–structure relationship of a model nanocomposite material". In Trends in Colloid and Interface Science XVII, 124–29. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/b94023.
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Ghosh, G., A. Vílchez, J. Esquena, C. Solans e C. Rodríguez-Abreu. "Preparation of Porous Magnetic Nanocomposite Materials Using Highly Concentrated Emulsions as Templates". In Trends in Colloid and Interface Science XXIV, 161–64. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-19038-4_29.
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Chen, Min. "Polymer/SiO2 Nanocomposite Colloids". In Mass Transport of Nanocarriers, 593–637. Pan Stanford Publishing, 2012. http://dx.doi.org/10.1201/b12528-17.
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"Nanocomposites". In Encyclopedia of Colloid and Interface Science, 733. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-20665-8_100105.
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Fu, Meng, Zepeng Zhang, Rui Jiang e Hongbao Liu. "Magnetic Assembly and Functionalization of One-Dimensional Nanominerals in Optical Field". In Clay and Clay Minerals [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.98908.
Testo completoAbstract (sommario):
Magnetic particles can be oriented along the magnetic field direction to achieve orderly arrangement under the magnetic field. Optical functional materials such as photonic crystal and liquid crystal can be obtained according to magnetic induced ordered nanostructure assembly. One-dimensional natural clay minerals with unique structure, composition and properties can be used as structural base to prepare anisotropic magnetic nanoparticles by decorated with magnetic particles, achieving unique optical functional properties. In this chapter, one-dimensional clay minerals@Fe3O4 nanocomposites were prepared by co-precipitation. The resulting one-dimensional clay minerals@Fe3O4 nanocomposites are superparamagnetic. They can be oriented along the direction of the magnetic field and produce an instantaneously reversible response. These magnetic mineral materials can be dispersed in a dilute acid solution to form stable colloid solutions. These stable colloid solutions produce a similar magnetically controlled liquid crystal with Bragg diffraction under an external magnetic field. Their optical properties are affected by magnetic field intensity, magnetic field direction and solid content. The results show that the functionalization of one-dimensional clay minerals has potential applications in display devices, photonic switches and other fields.
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"Polymer/SiO Nanocomposite Colloids: Synthesis, Characterization, and Their Applications". In Handbook of Innovative Nanomaterials, 619–42. Jenny Stanford Publishing, 2012. http://dx.doi.org/10.1201/b12707-31.
Testo completoAtti di convegni sul tema "Colloïde nanocomposite"
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Azouri, Assaf, Ming Ge, Kun Xun, Klaus Sattler, Joe Lichwa e Chittaranjan Ray. "Zeta Potential Studies of Titanium Dioxide and Silver Nanoparticle Composites in Water-Based Colloidal Suspension". In ASME 2006 Multifunctional Nanocomposites International Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/mn2006-17072.
Testo completoAbstract (sommario):
We determine the zeta potential (ZP) by using electrophoretic laser light scattering and Laser Doppler Velocimetry (LDV). Particle sizes are measured by photon correlation spectroscopy (PCS). We studied the ZP for colloidal suspensions of TiO2 and Ag metal particles in order to determine the kinetic interaction and charge exchange between the particles. We investigated the natural tendency of the particles for aggregation and varied the pH of the solution. It was found that the ZP versus pH curve for the mixed TiO2/Ag did not behave as the average of the individual TiO2 and Ag curves as one would expect, and instead there was a slight horizontal shift towards higher pH values which implies that the particles in the mixed TiO2/Ag colloid are interacting with the result of charge exchange. The average particle size was measured in terms of effective diameter, for the TiO2, Ag and the mixed TiO2/Ag particles. The results indicated an increase of approximately 100 nm in the effective diameter of the mixed TiO2/Ag particles size compared to the size of the individual TiO2 particles. This can be explained as the fact that 50 nm Ag particles are adsorbed on the surface of the TiO2 particles.
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Viorica, Railean, Anna Król-Górniak, Pomastowski Pawel e Buszewski Boguslaw. "New Consideration in Achievement of (Bio) Colloid Nanocomposites". In The 7th World Congress on Recent Advances in Nanotechnology. Avestia Publishing, 2022. http://dx.doi.org/10.11159/icnnfc22.176.
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