1,721,053 research outputs found
Elektrodokuma lifler üzerine konumlandırılmış: Yeni nesil metal katalizörler
No full textElektrodokuma liflerin oluşturduğu ağsı “nanoyapı”, birçok endüstriyel uygulama için vazgeçilmez bir özellik sunmaktadır. Son birkaç yıl içerisinde gerçekleştirilen akademik çalışlmalarda, bu lifsi yapıların yeni nesil katalitik ürünler için de umut vaat eden malzemeler arasında olduğu gösterilmektedir.
Katalizörler, bir kimyasal tepkimenin gerçekleşmesini tetikleyen, kolaylaştıran maddeler olarak tanımlanırlar. Her ne kadar günlük hayatta katalizörlerle karşılaşmasak da, aslında çokça kullandığımız
birçok ürünün katalizör kullanılmadan üretilmesi neredeyse imkânsızdır
Elektrodokuma lifler üzerine konumlandırılmış: Yeni nesil metal katalizörler
No full textElektrodokuma liflerin oluşturduğu ağsı “nanoyapı”, birçok endüstriyel uygulama için vazgeçilmez bir özellik sunmaktadır. Son birkaç yıl içerisinde gerçekleştirilen akademik çalışlmalarda, bu lifsi yapıların yeni nesil katalitik ürünler için de umut vaat eden malzemeler arasında olduğu gösterilmektedir.
Katalizörler, bir kimyasal tepkimenin gerçekleşmesini tetikleyen, kolaylaştıran maddeler olarak tanımlanırlar. Her ne kadar günlük hayatta katalizörlerle karşılaşmasak da, aslında çokça kullandığımız
birçok ürünün katalizör kullanılmadan üretilmesi neredeyse imkânsızdır
AMWC 2013: Advanced Materials World Congress (İzmir, Turkey, September 16–19, 2013)
Get PDFRecent decades witnessed an explosion of new materials and new ways to fabricate and use naturally occurring and engineered materials. Scientists and engineers from various fields refer to this development to understand materials structure fundamentally and accordingly material properties and function. Currently, it is crucial to provide a global platform for researchers and engineers from both academia and industry to present their research results and activities with a special attention from an
interdisciplinary aspect of advanced materials
10. A recycling route of plastics via electrospinning: from daily wastes to functional fibers
No full textInvestigation on glassy skin formation of porous polystyrene fibers electrospun from DMF
Get PDFMicrometer and submicrometer diameter of polystyrene (PS) fibers were electrospun from various dimethyl formamide (DMF) solutions at different weight fractions under 35% relative humidity. Increasing polymer fraction in the solution results in a gradual morphological transition from beads-with-incipient to bead-free fibers and also increases the diameter. The formation of uniform glassy skin presumably due to radial capillary flow within the liquid jet was confirmed by scanning electron microscope. The thickness of the skin varies with the weight fraction of PS; therefore, it was normalized with respect to average fiber diameter (AFD). The skin gets thinner as the weight fraction of PS increases. In addition, the fibers exhibit highly porous internal structure and smooth surface along with slight porosity. The development of porosity is attributed to liquid-liquid phase separation of water molecules in atmospheric moisture and DMF.TÜBİTAK TBAG-107T79
Toward transparent nanocomposites based on polystyrene matrix and PMMA-grafted CeO 2 nanoparticles
Get PDFThe association of transparent polymer and nanosized pigment particles offers attractive optical materials for various potential and existing applications. However, the particles embedded into polymers scatter light due to refractive index (RI) mismatch and reduce transparency of the resulting composite material. In this study, optical composites based on polystyrene (PS) matrix and poly(methyl methacrylate) (PMMA)-grafted CeO 2 hybrid particles were prepared. CeO 2 nanoparticles with an average diameter of 18 ± 8 nm were precipitated by treating Ce(NO 3) ·6H 2O with urea in the presence of a polymerizable surfactant, 3-methacyloxypropyltrimethoxy silane. PMMA chains were grafted on the surface of the nanoparticles upon free radical in situ solution polymerization. While blending of unmodified CeO 2 particles with PS resulted in opaque films, the transparency of the composite films was remarkably enhanced when prepared by PMMA-grafted CeO 2 hybrid particles, particularly those having a PMMA thickness of 9 nm. The improvement in transparency is presumably due to the reduction in RI mismatch between CeO 2 particles and the PS matrix when using PMMA chains at the interface.TÜBİTAK TBAG-109T90
Anomalous transmittance of polystyrene-ceria nanocomposites at high particle loadings†
Get PDFOptical nanocomposites based on transparent polymers and nanosized pigment particles have usually been produced at low particle concentrations due to the undesirable optical scattering of the pigment particles. However, the contribution of the particles to many physical properties is realized at high concentrations. In this study, nanocomposites were prepared with transparent polystyrene (PS) and organophilic CeO2 nanoparticles using various compositions in which the particle content was up to 95 wt%. The particles, capped by 3-methacryloxypropyltrimethoxysilane (MPS), were dispersed into PS and the transmittance of the spin-coated composite films was examined over the UV-visible region. When the particle concentration was <20 wt%, the transmittance of the films showed a first-order exponential decay as the Rayleigh scattering theory proposes. However, a positive deviation was observed from the decay function for higher particle contents. The improvement in transmittance may be a consequence of interference in the multiple scattering of light by the quasi-ordered internal microstructure that gradually develops as the particle concentration increases.TÜBİTAK (TBAG-109T905
Dispersion of organophilic Ag nanoparticles in PS-PMMA blends
Get PDFAbstract The preparation of stable composites with well-controlled particle location is one of the challenges in formulating new polymer/nanoparticle mixtures. In this study, cetyltriammonium bromide (CTAB)-capped monodisperse Ag nanoparticles were prepared and mixed with an equimass blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA) in solution. The surface of the blend film without nanoparticles showed spherical pits with a size of 4.5 μm in diameter. The integration of CTAB-capped nanoparticles into the blend film developed surface bumps with a size of 0.4 μm in diameter. The organophilic Ag nanoparticles were distributed heterogeneously in the immiscible PS-PMMA blend. When the diameter of particle domains reached approximately 20 nm, particles were preferentially located at the interface of the PS and PMMA domains. Larger particle domains with a diameter of 90 nm were found to be in the PMMA-rich phase. Isothermal post-treatment of the PS-PMMA/Ag composite films directs the particle domains into PS domains. Thermodynamic factors that contribute to the observed morphologies are discussed.Turkish Academy of Sciences (TÜBA-GEB_IP 2013
Dimensions of polystyrene particles deposited on mica from dilute cyclohexane solution at different temperatures
Get PDFUsing atomic force microscopy, the height, diameter, and volume of polystyrene particles deposited on mica from dilute cyclohexane solution at different temperatures are determined. Dimensions exhibit a strong temperature dependence. The heights of the deposited particles are only a few atomic diameters, the major dimension being parallel to the mica surface. The number of single polystyrene molecules in a deposited particle cannot be determined directly by atomic force microscopy. However, the maximum number of molecules that may be present in a particle may be estimated, Below 35 degreesC, the particles possibly consist of single collapsed molecules. This number increases with temperature and becomes as large as about 30 molecules per particle at 80 degreesC. The volume occupied by a single chain in solvent is calculated as a function of temperature and compared with observed volumes of dry particles on mica. A linear relationship is observed between single chain volumes in solvent and corresponding particle volumes on mica. On the average, the volume of a single chain in solution is 10 times the volume of a dry particle at the corresponding temperature. Fluctuations of chain volumes that are dominant in solution are also present in the volumes of particles deposited and dried on mica
Formation of Pseudoisocyanine J-Aggregates in Poly(vinyl alcohol) Fibers by Electrospinning
Get PDFSubmicrometer diameter, light emitting fibers of poly(vinyl alcohol) (PVA) doped with pseudoisocyanine
(1,1′-diethyl-2,2′-cyanine bromide, PIC) dye were prepared by electrospinning. A horizontal setup was employed
with a stationary collector consisting of two parallel-positioned metal strips separated by a void gap. Formation
of uniaxially aligned and randomly deposited fibers in electrospun films was confirmed by microscopy.
Photoluminescence (PL) spectroscopy is used to evaluate spectral properties of both types of fibers doped
with PIC. While PIC molecules were individually dispersed in PVA solution, they assemble into J-aggregates
upon electrospinning when the weight fraction of PIC molecules is above 2.5 wt %. The formation of
J-aggregates was observed in both randomly deposited and uniaxially aligned electrospun fibers. Moreover,
the fibers aligned uniaxially showed a high degree of polarized emission (PL
|/PL⊥)10), arising from the
orientation of J-aggregates along the fiber axis. On the other hand, isotropic emission of J-aggregates was
observed from the fibers deposited randomly. As a conclusion, electrospinning was found to be an efficient
and a practical method to form highly oriented J-aggregates dispersed into polymer fibers. To the best of our
knowledge, it is the first time formation of J-aggregates (a bottom-up approach) and electrospinning (a topdown approach) is successfully combined
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