Enhanced Power Factor of PANI/GNP nanocomposites

Comunicación presentada en la 11th European Conference on Thermoelectrics (ECT2013), celebrada en Noordwijk (Holanda) del 18 al 20 de noviembre de 2013.Nowadays, the inorganic compounds (like Bi2Te3) are the best thermoelectric materials due to their suitable thermoelectric properties for room temperature applications. Nevertheless, organic materials, like conjugated polymers, are becoming more important recently due to their increasing Figure of Merit (0.25‐0.42). Polymers generally have low thermal conductivity (©§≈0.1‐0.5W/m∙K), flexibility, environmental stability, easily doping and de‐doping, non‐toxicity, potential processing advantages (e.g. printing) and straightforward preparation in comparison with inorganic semiconductors. The increase in the Power Factor of this materials, which is given by S2¥ò, is being achieved by two mechanisms: doping the polymers or blending them with different kinds of filling materials, such as carbon nanotubes, graphene nanosheets (GN) or graphene nanoplatelets.Peer Reviewe

Synthèse et étude de systèmes moléculaires pour la réalisation de diodes électroluminescentes organiques monocouches

MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Room temperature ionic liquids versus organic solvents as lithium-oxygen battery electrolytes

Imidazolium, pyrrolidinium and piperidinium room temperature ionic liquids (RTILs) are characterized to evaluate their thermal stability, ionic conductivity, viscosity, potential window and lithium solvation, which are key parameters for lithium-oxygen (Li-O) battery electrolytes. The electrochemical tests of these RTILs are also carried out in Li-O cells and show reasonable values of specific capacity, up to 1659 mA h per gram of carbon in the case of 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (PMI TFSI) with a molar fraction of 0.2 of LiTFSI. RTILs are compared with conventional organic electrolytes like ethylene carbonate (EC)/diethyl carbonate (DEC) solution or tetraethylene glycol dimethyl ether (TEGDME), which enables us to provide a further insight into ways of improving the electrolyte properties of Li-O batteries. In particular, a viscosity lower than 100 cP combined with a lithium coordination number lower than 1.5 tends to enhance the battery performance

How abrupt change in surface temperature impacts water balance over France? A case-study of bread wheat cultivated areas.

International audienceAgricultural risk management is a major challenge for decision makers, public authorities and agricultural insurance companies, as crop losses linked to climate hazard are expected to increase in the context of climate change (Boucher et al., 2019). The present work is part of a PhD in partnership between Groupama insurance company (Domaine Assurance Récolte) and Biogeosciences laboratory (University of Burgundy). This collaborative research aims at depicting how, with the abrupt surface temperature warming, climate hazard evolution has affected water balance over France, and related agro-climatic risks.Since 1980s over western Europe, the warming trend intensifies strongly, consistent with climate simulations including anthropogenic forcing (Terray & Boé, 2013). As a result of this warming tendency, a shift is detected in maximum and minimum air temperature, delimiting two main climate periods: 1959-1987 and 1988-2009 (Brulebois et al., 2015). Along with this abrupt warming, a trend towards stagnation of crop yields is observed since the 1990s. Bread wheat yields are particularly affected. Yet this crop represents an important part of insured areas. In addition to maize and grapevine, the impact of climate hazard and agro-climatic risk on the evolution of bread wheat yields is a major issue for agricultural insurance companies. What are the patterns of water cycle responses to abrupt changes in temperature? Beyond that, how did surface warming shift impact water balance over main french bread wheat production basins?Clearly, quality and reliability of surface climate data sets remain an issue for the assessment of water cycle component changes. The SIM (Safran-Isba-Modcou) dataset of reanalysed surface meteorological observations offers the opportunity to address the complexity of processes leading to changes in local water cycle (Soubeyroux et al., 2018). With an 8km spatial resolution at daily time step, SIM interpolated precipitation and computed PET (Potential EvapoTranspiration) and AET (Actual EvapoTranspiration) from 1959 to 2019 data are relevant to this aim. Water balance is computed using a two-reservoirs model (Jacquart & Choisnel, 1995), and SIM climate data and bread wheat agronomic parameters as inputs. To focus on bread wheat production basins, only SIM grid point containing at least 10% of surface covered with bread wheat fields are retained. Regions of interest are selected and characterized through a teamwork with the insurance company collaborators.Our results suggest that the abrupt shift in air temperature in 1987/88 had a strong influence on the water cycle variables evolution. Water balance decreased on the post-shift period, along with the increase of water demand and soil drying. Consequently, water constraints increased fastly at the end of the 1980s, both annual and seasonal scale. Along with various seasonal evolution, changes in the hydrological cycle hide geographical disparities over France.Evolving climate hazard linked to water balance impacts agro-climatic risk, identified as one of the main factor affecting the evolution of bread wheat yields. Such conclusions suggest that, with both mean and variability changes in water balance state, probability to overcome risk threshold changes. This is of major concern for our partners, and may lead to adaptation process from managers

Nanomateriales en limpiadores de superficies duras

It is very common to find the presence of nanomaterials in consumer products to improve their targeted properties as well as to increase the functionality and efficiency. This review summarizes the cleaners that include nanomaterials present in the market. On the other hand, references about the potential eco-toxicities of nanomaterials are analyzed. There are some regulations in some areas, although the lack of legislation in this topic reflects the lack of knowledge about their potential toxicity both in life and in the environmentCada vez es más común encontrar la presencia de nanomateriales en los productos de gran consumo, ayudando a mejorar las propiedades deseadas, así como incrementando su versatilidad y eficacia. Este artículo presenta un resumen de los limpiadores con nanomateriales presentes en el mercado, junto con las propiedades que están ayudando a conseguir. Por otra parte, se analiza la literatura existente sobre estos nuevos materiales. Actualmente ya existen algunas normativas al respecto en algunos ámbitos, aunque la falta de legislación también refleja la falta de conocimiento sobre su posible toxicidad en los seres vivos y el medio ambiente

Suitability of Blended Ionic Liquid‐Dimethylsulfoxide Electrolyte for Lithium‐Oxygen Battery

Electrolytes composed of dimethylsulfoxide (DMSO), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI TFSI) and LiClO are characterized for application in lithium-oxygen batteries. The increase of EMI TFSI content in the electrolyte enables to improve its thermal stability and to decrease the overpotential of the cell. The optimum addition of EMI TFSI enables to reduce the overpotential from 1.43 V to 1.06 V, with a cyclability of 69 cycles with 600 mAh g of limited capacity

Silole derivatives: relationships between molecular arrangement and OLED efficiency.

International audienceThe goal of the present study is to underline the relationships that may exist between the molecular arrangement in thin films and the OLED efficiency. For this purpose, we have synthesized three new silole derivatives with incrementally flexible structure to tune their packing ability. Moreover, these siloles were especially designed to possess both electron-and hole-transporting properties in order to be used in single-layer OLEDs. This architecture was chosen since the absence of organic layers interfaces allows a better evaluation of the role of the molecular arrangement in the active layer. The examination of the EL properties gives evidences of the prominent role of the molecular organization on the OLED efficiency. A crystalline-like organization of the molecules allows high current density but low luminance efficiency since an excessive electron current flow is involved compared to the hole one, and the recombination rate is poor. On the contrary, disordered assemblies of molecules allows better performances by avoiding unfavorable p-stacking, while keeping good intermolecular orbital overlaps to support charge carrier transport. Thus single-layer devices based on silole 9 exhibit luminance efficiency as high as 0.75 Cd/A associated with both good chemical and film stabilities that are very promising applications for long life OLED application

How abrupt change in surface temperature impacts water cycle over France ?

International audienceAlong with the rapid warming tendency of the last decades over France, a shift in air temperaturehas been detected in 1987/88, delimiting two main climate periods from 1959 to 2019. Evidence of pre- andpost-shift runoff seasonal differences suggest an impact of this abrupt warming on water cycle evolution. Asyearly precipitation slightly evolve during the studied period, evapotranspiration appears to be one of themain drivers of the hydrological cycle evolution. Spring is marked by a strong increase in evaporativedemand, followed in summer by a rise in water stress and a drying of soil water content. Besides temporaldisparities, this local water cycle evolution depicts different spatial responses over France. Modifications ofclimate hazard linked to water cycle is expected to impact agro-climatic risks and crop yields