Epitaxial bilayer La0.7Sr0.3MnO3/Ba0.7Sr0.3TiO3 thin films obtained by polymer assisted deposition

In this work bilayer structures, composed of ferromagnetic manganite and ferroelectric titanate layers, were obtained by solution deposition technique. The first step in preparation of the bilayer thin films was deposition of manganite (LaMnO3 or La0.7Sr0.3MnO3) layer by water-based polymer assisted deposition (PAD). Polycrystalline structures were obtained when manganite films were deposited by spin coating on commercial Pt/TiO2/SiO2/Si type substrate, whereas epitaxial films were grown on a single crystal SrTiO3 with (001) orientation substrate. The second ferroelectric titanate (BaTiO3 or Ba0.7Sr0.3TiO3) layer was deposited by spin coating using sol-gel method. The obtained bilayer structures have thickness below 100 nm, and epitaxial growth of the Ba0.7Sr0.3TiO3 film on the La0.7Sr0.3MnO3 surface was obtained, due to the similar lattice parameters between these two crystal structures

A film-forming graphene/diketopyrrolopyrrole covalent hybrid with far-red optical features: Evidence of photo-stability

A dianiline derivative of a symmetric donor-acceptor-donor diketopyrrolopyrrole-based dye is employed for the two-sided covalent functionalization of liquid exfoliated few layers graphene flakes, through a direct arylation reaction. The resulting nanohybrid features the properties of a polymeric species, being solution-processed into homogeneous thin films, featuring a pronounced red-shift of the main absorption band with respect to the model dye unit and energy levels comparable to those of common diketopyrrolopyrrole-based polymers. A good electrical conductivity and the absence of radical signals generated after intense white light illumination, as probed through electron paramagnetic resonance, suggest a possible future application of this composite material in the field of photoprotective, antistatic layers with tunable colors

Studies on the thermal decomposition of multiwall carbon nanotubes under different atmospheres

Carbon nanotubes (CNTs) have unique physical properties. This has been the driver for the current exploitation of their use in different advanced applications, such as in composite nanoscale devices. If a thermal treatment is required for the fabrication of the composite, the thermal decomposition behavior of the tubes is a key aspect in the integration process. Within this context, the thermal decomposition of multiwall CNTs (MWCNTs) under different conditions was studied in this work by DTA/TG, XRD, RAMAN spectroscopy and electron microscopy. Purified MWCNTs are stable up to 420 T in air, as no weight loss occurs in TG/DTA analysis under non isothermal conditions but morphology changes were observed for isothermal conditions at 400 degrees C by Raman spectroscopy. In oxygen-rich atmosphere MWCNTs started to oxidized at 200 degrees C. However in argon-rich atmosphere and under a high heating rate MWCNTs remain stable up to 1300 degrees C with a minimum sublimation. The activation energy for the decomposition of MWCNTs in air was calculated to lie between 80 and 108 kJ/mol. These results have broad implications for the expanded use of MWCNTs in composites with functional complex oxides that usually require synthesis temperature above 650 degrees C. 2012 Elsevier B.V. All rights reserved

Characterization of CNT Enhanced Conductive Adhesives in Terms of Thermal Conductivity

CNTs have excellent thermal, electrical and mechanical properties. They can be used in various ways. One researched field of application is CNT-polymer composites which combine common technologies with advanced materials. This paper will focus on the thermal property of CNT-Ag-filled adhesives and compares the new materials with conventional, electrical Ag-filled conductive adhesives. Several analytical methods, FTIR, Raman analysis, SEM and TEM have been carried out to examine the different surface conditions after physicval and chemical modification of CNTs. The thermal conductivities of composites containing different types of CNTs were investigated. The incorporation of CNTs into polymers resulted in enhancement of the thermal conductivity compared to Ag-filler. The increase of thermal conductivity with addition of CNT filler is obvious, especially for the purified CNT. The value of thermal conductivity is about two times higher than the Ag-filled conductive adhesive. However, improvement on thermal conductivity of the surface modified CNT-filled conductive adhesives is not so obvious. Since the thermal conduction in CNT is by phonon transfer, the nanometric size and the huge interface lead to strong phonon-scattering at the interface. Thus, a relatively low interfacial area, weak interfacial adhesion promotes the conduction of phonons and minimizes coupling losses. According to this, the non-treated MWCNTs seem to have the highest potential to improve the thermal conductivity of epoxies

Electron Microscopy Investigation of Coated Multiwall Carbon Nanotubes Prepared by Reactive Ball Milling

Homogeneous and stable inorganic coating of SiO2, Al2O3 and TiO2 was obtained on the surface of multiwall carbon nanotubes (MWNTs) by mechanically mixing them with precursor compounds in a planetary ball mill and by subsequent hydrolysis. Detailed studies by means of transmission and scanning electron microscopy revealed that the milling time as well as the number of balls significantly affects the homogeneity of the layer formed. Our results demonstrate that planetary ball milling can be an effective and low-cost process for the production of homogenous coating of oxides on MWNTs in a large-scale

Preparation of homogeneous titania coating on the surface of MWNT

Preparation of homogeneous and stable inorganic coatings on the surface of multi-wall carbon nanotubes (CNTs) was studied. Precursor compounds such as titanium (IV) bromide and titanium (IV) chloride were used to cover the surface of CNTs under either solvent-free or solution conditions. As-prepared titania layers were characterized by transmission, scanning electron microscopy and X-ray diffraction techniques. Results revealed that homogenous coverage can be achieved in a controllable way. (C) 2010 Elsevier Ltd. All rights reserved

Composites of ion-in-conjugation polysquaraine and SWCNTs for the detection of H2S and NH3 at ppb concentrations

Abstract Several different methods are established for the analysis of gases, including optical spectroscopy, photoacoustic spectroscopy as well as colorimetric and resistive sensing, the measurements systems are either too complex or have limited sensitivity. In particular, when the goal is to apply a large number of sensors in networks, it is highly desirable to have devices that are simple, have low cost and energy consumption, yet sensitive and selective to monitor analytes even in traces. Herein, we propose a new type of resistive sensor device based on a composite of single-wall carbon nanotubes and an ion-in-conjugation polymer, poly(1,5-diaminonaphthalene-squaraine), capable of detecting H2S and NH3 in air even at room temperature with a theoretical concentration limit of ∼1 ppb and ∼7 ppb, respectively. Density functional theory calculations revealed that H atoms of the analytes and O atoms of the polymer chain interact and form hydrogen bonds, and the electron withdrawal from the gas molecules by the polymer chain results in the change of its electrical conductivity. To demonstrate the feasibility of the new nanocomposites in sensing, we show the devices for monitoring food safety with good sensor stability of operation for at least 3 months of period of time

Effect of sonication time on the synthesis of the CdS nanoparticle based multiwall carbon nanotube - maleic anhydride-1-octene nanocomposites

Effect of sonication time on the synthesis of the CdS nanoparticles within the matrix obtained through the covalent functionalization of multiwall carbon nanotube (MWCNT) with maleic anhydride (MA) - 1-octene copolymer was investigated. Cadmium chloride and thiourea were used as the raw materials. MWCNTs used for the matrix were synthesized by Catalytic Chemical Vapor Deposition using Fe-Co/Al2O3 as the catalyst. The obtained nanostructures were characterized by FTIR, XRD, Raman spectroscopy, TEM, SEM, TG and UV-Vis spectroscopy. Electrophysical properties of the polymer nanocomposites obtained using different periods of time for sonication were comparably investigated. The average CdS particle diameter was between 3.9-7.9nm as confirmed independently by TEM and XRD. UV-Vis spectroscopy revealed that the obtained nanostructures are appropriate base materials for making optical devices

Preparation of homogeneous titania coatings on the surface of MWNTs

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