Search results for "composites"

Photochemical stabilization of LLDPE/clay nanocomposites: towards durable nanocomposites

2008

This article reports a study of the chemical modifications of LLDPE/nanoblend nanocomposites exposed to UV light in conditions of artificially accelerated ageing and natural weathering. Analysis by infrared spectroscopy of the chemical modifications produced by photoageing shows that the presence of an organo-clay leads to the decrease of the oxidation induction time of the polymer (LLDPE), which results in lower durability of the nanocomposites. Protection against photooxidation was tested with different kinds of UV stabilizers and with a metal deactivator. It is shown that the metal deactivator is very efficient in stabilizing the nanocomposite since it totally cancels the prodegradant ef…

Photo-oxidation resistance of polyethylene/carbon nanotubes composites: aspect ratio and surface functionalization effect

2012

PHOTO-OXIDATION OF PA6/GRAPHENE OXIDE FILMS

2014

Graphene oxide (GrO) was synthesized with Marcano’s method [1] and added at 0.5 and 1 wt% loading content to a polyamide 6 (PA6). In particular, three different techniques have been used for the preparation of the nanocomposites: (i) melt blending in a batch mixer, (ii) solvent casting in formic acid, (iii) preparation of a masterbatch by solvent casting and further melt processing. The films (80 m) were photo-oxidized in a QU-V chamber up to about 100 hours. The effect of filler content and preparation technique on the photo-stability of the nanocomposites has been followed by monitoring the change of the mechanical and spectroscopic properties undergone upon artificial exposure to UV-B l…

Photo-oxidation of nano- and micro-filled polypropylene

2010

Photo-oxidation of polyolefin/clay nanocomposite films: role of organoclay and matrix type

2009

Comparison of the electrochemical properties of hematite thin films prepared by spray pyrolysis and electrodeposition

2015

Abstract This manuscript reports differences between the photoelectrochemical (PEC) activity of hematite (α-Fe 2 O 3 ) photoanodes produced by cathodic electrodeposition (ED) and spray pyrolysis (SP) methods. Both methods yield nanostructured polycrystalline α-Fe 2 O 3 thin films without additional impurity phases. However, α-Fe 2 O 3 produced by ED is characterised to have better crystallinity and higher porosity, which was confirmed by XRD and SEM analysis. Owing to this, α-Fe 2 O 3 obtained by ED generates a photocurrent that is 2.5 times higher than α-Fe 2 O 3 thin films prepared by SP. Furthermore, the influence of the thickness of the α-Fe 2 O 3 thin films on the flat-band potential p…

Pyrene-benzoylthiophene Bichromophores as Selective Triplet Photosensitizers.

2006

Combination of the pyrene and benzoylthiophene units constitutes an interesting approach to design bichromophoric photosensitizers with increased intersystem crossing quantum yield and enhanced selectivity. The potential of this strategy has been illustrated in the present work by using a model photoisomerization reaction.

Photoluminescence activity in natural silica excited in the vacuum-UV range

1999

Abstract We report an experimental study on the optical absorption and photoluminescence detected in samples of natural silica. Our results show that the two emission bands, β (∼3.1 eV) and α E (∼4.3 eV), have an excitation profile in the vacuum ultraviolet region with a maximum at ∼7.5 eV. This excitation profile indicates that, in terms of energy levels of the luminescent defect, there is a transition from a ground state, S 0 , to a second excited state, S 2 , able to excite PL emission, in addition to the well known transition corresponding to the optical absorption band, B 2β . Our data are in a quantitative agreement with `ab initio' calculations carried out for a two-fold coordinated …

Formation of optically active oxygen deficient centers in Ge-doped SiO2 by γ- and β-ray irradiation

2010

Abstract We report an experimental study on the comparison between the γ- or β-ray induced Ge related point defects in Ge-doped silica. Silica samples doped with ∼2.2 1017 Ge atoms/cm3 produced with the sol–gel technique have been irradiated with γ-ray or with β-ray. The effects of the irradiation have been investigated by optical absorption, photoluminescence and electron paramagnetic resonance spectroscopy in order to evaluate the generation and the dependence on dose of the Ge(1), E’Ge, GLPC (Germanium lone pair center) and H(II) point defects. No relevant differences between the concentrations of γ- or β-ray induced Ge(1) and E’Ge point defects have been observed and, in addition, it ha…

Absorption and luminescence in amorphous silica synthesized by low-pressure plasmachemical technology

2007

A comparison study of as-deposited by the hydrogen-free SPCVD process silicon dioxide with and without fluorine as well as the one in the form of fused materials is performed to define whether glass forming processing affects its optical properties. Raman scattering, optical absorption in the vacuum ultraviolet region as well as luminescence at different temperatures and various excitation conditions are measured. A difference in Urbach rule parameters and intrinsic defect concentrations for different samples is revealed. No significant impact on the structure responsible for Raman scattering is observed.