Effects of single-walled carbon nanotubes on the optical and photo-conductive properties of their composite films with regio-regular poly(3-hexylthiophene)

The effect of a small admixture of single-walled carbon nanotubes (SWNTs) HiPCO (high pressure carbon monoxide) (from 0.5 to 2 wt%) on the supramolecular structure in regio-regular poly(3-hexylthiophene) (RR-P3HT) thin films is studied and their optical and photoconductivity properties are investigated. It is demonstrated that the presence of such small amounts of nanotubes improves the structural organization in the films as evidenced by X-ray diffraction (XRD) studies. This is confirmed by UV–visible optical absorption investigations which clearly show a better conjugation of P3HT in the presence of nanotubes. In Raman spectra of composites, changes in intensities and frequencies of the radial breathing modes are observed upon addition of nanotubes. This can be rationalized by a modification of the resonance conditions caused by a selective dispersion and wrapping of SWNTs via π-interaction (π-stacking). As a consequence of these interactions, a dramatic photoluminescence (PL) quenching is observed which becomes more and more pronounced with increasing the nanotube content. This implies a fast photo-induced electron transfer favoured by a large area of the SWNTs/P3HT interface and strong interactions between these two components. An increase in the composite photocurrent by at least one-order of magnitude, as compared to the case of pure P3HT film, is the most pronounced effect of this electron transfer. These two effects are of crucial importance for the application of the investigated composites in bulk hetero-junction photovoltaic cells (BHJPCs) and organic photo-detectors (OPDs).     

Influence of the history of a melt on the electrical resistivity of cadmium–antimony liquid alloys

Miller, Paces and Komarek (MPK) [Trans. Metall Soc. AIME 230 (1964) 1557] observed an influence of the history of a melt on the electrical resistivity of several cadmium–antimony alloys. In this work we complete the experimental work of MPK with new accurate experiments in order to verify the existence of the phenomenon and to precise by defining the conditions where it appears. We used three important improvements on the experimental design of MPK. First we used quartz cells instead of pyrex cells used by MPK so allowing the heating of the melt well above the temperature of 530 °C attained by MPK. Secondly our experimental design allows to mix mechanically the liquid alloy in order to achieve a macroscopic homogeneity of the melt. Finally we measure simultaneously the thermopower of the Cd₆₀–Sb₄₀ liquid alloy. The time evolution of our experiment is fully described with our conclusions.     

Combining Soft Chemistry and Spark Plasma Sintering to Produce Highly Dense and Finely Grained Soft Ferrimagnetic Y3Fe5O12 (YIG) Ceramics

We report the synthesis of yttrium iron garnet (YIG) combining soft chemistry route, namely the polyol process, and spark plasma sintering (SPS) technique. The polyol process produced an intermediary amorphous phase containing both iron and yttrium cations in the desired ratio. They were annealed at 400°C in air to decompose the organic content of the reaction (polyol and acetate). To achieve the garnet phase, the polyol‐obtained precursor was subjected to reactive SPS treatment at a temperature of 750°C, far below the typical temperatures (1350°C) used in the classic solid‐state reaction process. In 15 min pure and high‐density Y₃Fe₅O₁₂ ceramic, with about 100 nm sized crystalline grains, was obtained. We report as well the characterization of the initial amorphous phase and the obtained YIG by X‐ray diffraction, scanning electron microscopy, Fourier‐transform infrared spectroscopy, ⁵⁷Fe Mössbauer spectrometry, and magnetization measurements.     

Mechanical and thermal properties of compatibilized polypropylene reinforced by woven doum

In this work, the development and the mechanical characterization of a doum textile composite based on a polypropylene matrix were carried out. Mechanical and rheological tests were effectuated, to illustrate the effect of woven fibers on the mechanical and viscoelastic properties at 0°, 15°, 30°, and 45° directions. The woven fibers were treated and the matrix was melted to a coupling agent to assure compatibility between the fibers and the polymer. The composites with long fiber are generally used as film and the main properties is the tensile. In this study, our goal was to improve the tensile properties. Results have shown that tensile properties exhibited a significant increase when compared to the polypropylene. However, it was observed that the stress direction has no influence on the thermal properties of the composite. Also, this article evaluates models that predict the stiffness of the composites at different stress directions to be compared to the experiments. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4347–4356, 2013     

Dynamic analysis of a rigid rotor supported by three-pad hydrostatic squeeze film damper lubricated with ferrofluid

This work describes an analytical study on the dynamic behaviour of a three-pad hydrostatic journal bearing lubricated with ferrofluids. Each pad is fed with an external pressure through a capillary restrictor-type hydraulic resistance. Ferrofluid or magnetic fluid is a colloidal dispersion of magnetic nano-particles in a carrier liquid. In this study, a non-linear method was performed using Jenkins model in order to investigate the effect of ferrofluids lubrication on the vibrations amplitude and the transmitted forces of hydrostatic squeeze film dampers. The results presented in this paper showed that the ferrofluid lubrication is useful in controlling the bearing vibrations and transmitted forces. The results illustrated in this work are expected to be quite useful to the bearing designers.     

Experimental investigation of the effects of a compatibilizing agent on the properties of a recycled poly(ethylene terephthalate)/polypropylene blend

This study deals with the behavior of a recycled polyethylene terephthalate (PET)/polypropylene (PP) blends. The compatibilizing effect has been investigated to examine the recycling feasibility in industrial production. The compatibilizing efficiency of olefinic copolymers containing epoxy groups for a/polypropylene (PET/PP) blends was examined using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), mechanical testing and rheological one. The effect of ethylene-glycidyl methacrylate (E-GMA, 92/8 wt%, Lotader AX8840) and ethylene–methyl acrylate-glycidyl methacrylate (E-MA-GMA, 68/24/8 wt%, Lotader AX8900) copolymers was investigated. The blends of PET/PP/compatibilizer at compositions 80/15/5, 85/11.25/3.75, 90/7.5/2.5 and 95/3.75/1.25 (wt%) were prepared by melt mixing in a single-screw extruder. Test specimens were prepared by compression moulding at processing temperatures of 250 °C. The incorporation of the compatibilizers has a large effect on the dispersion of the PP phase. Moreover, the copolymer was more efficient than the terpolymer. Especially, E-GMA was found to improve the elongation at break of the blends containing 80 % PET.     

Interaction of uranium with in situ anoxically generated magnetite on steel

In the high level nuclear waste repository concept, spent nuclear fuel is designed to be encapsulated in steel canisters. Thus, it is necessary to study the influence of the steel and/or its corrosion products on the behaviour of the radionuclides released from the fuel. In this sense, the main objective of this work is to contribute to the knowledge of the influence of the steel and/or its corrosion products on the uranium(VI) retention. To this aim, magnetite (Fe(3)O(4)) has been generated by anaerobic steel corrosion in an autoclave reactor at an overpressure of 8atm of H(2)(g). After characterisation by X-ray diffraction (XRD), the obtained corroded steel coupons were contacted, at two different H(2)(g) pressures (1atm and 7.6atm), with a U(VI) solution. The evolution of the uranium concentration in solution is determined and a study of the composition of the coupons at the end of the experiments is carried out. The main conclusion obtained from this work is that magnetite generated on a steel coupon is able not only to retain uranium via sorption, but also to reduce hexavalent to tetravalent uranium in a higher extent than commercial magnetite, thus, providing an effective retardation path to the migration of uranium (and, potentially, other actinides) out of the repository.     

The relationship between pollutant emissions,renewable energy,nuclear energy and GDP: empirical evidence from 18 developed and developing countries

This document investigates the causal relationship between nuclear energy (NE), pollutant emissions (CO₂ emissions), gross domestic product (GDP) and renewable energy (RE) using dynamic panel data models for a global panel consisting of 18 countries (developed and developing) covering the 1990–2013 period. Our results indicate that there is a co-integration between variables. The unit root test suggests that all the variables are stationary in first differences. The paper further examines the link using the Granger causality analysis of vector error correction model, which indicates a unidirectional relationship running from GDP per capita to pollutant emissions for the developed and developing countries. However, there is a unidirectional causality from GDP per capita to RE in the short and long run. This finding confirms the conservation hypothesis. Similarly, there is no causality between NE and GDP per capita.