The Regulation of Ion Homeostasis, Growth, and Biomass Allocation in Date Palm Ex Vitro Plants Depends on the Level of Water Salinity

The date palm, a central plant in the fragile oasis ecosystem, is considered one of the fruit species most tolerant to salt stress. However, the tolerance mechanisms involved are yet to be addressed and their evaluation until now was mainly based on heterogenous plant material such as seedlings or limited to in vitro experiment conditions. For these reasons, we propose to deepen our knowledge of the morphological and physiological responses to salt stress using acclimated ex vitro plants resulting from the propagation of a single genotype. The plants were irrigated with 0, 150, 300, or 450 mM NaCl solutions for four months. Our results showed that the influence of water salinity on growth and ion-homeostasis regulation was very dependent on stress levels. The 150 mM NaCl concentration was found to improve dry biomass by about 35%, but at higher salt concentrations (300 and 450 mM) it decreased by 40–65%. The shoot:root dry mass ratio decreased significantly at the 150 mM NaCl water concentration and then increased with increasing water salt concentration. The leaf:root ratio for Na+ and Cl− decreased significantly with increasing water salinity up to a concentration of 300 mM NaCl, and then stabilized with similar values for 300 mM and 450 mM NaCl. In contrast to Na+ and Cl−, leaf K+ content was significantly higher in the leaf than in the root for all salt treatments. Unlike Na+ and K+, Cl− was expelled to the surface of leaves in response to increased water salinity. Overall, date palm plants appear to be more capable of excluding Cl− than Na+ and of changing biomass allocation according to salt-stress level, and their leaves and roots both appear to play an important role in this tolerance strategy.All authors are funded through the Small Research group project from the Deanship of Scientific Research at King Khalid University under research grant number (R.G.P.1/295/43).Peer reviewe

Tribological properties of Ni–B–TiO2 sol composite coating elaborated by sol-enhanced process: abrasive wear and impact wear

The development of composite coating with higher dispersive second phase is a crucial goal to achieve its performance against wear. In this respect, an interesting experimental investigation on the behavior of Ni–B–TiO2 sol composite coating towards scratching, sliding and impact loadings was performed. The adhesive strength was determined by progressive scratch test, while the tribological behavior was assessed through rotating and reciprocating sliding tests, as well as the impact-sliding tests. The in-situ formation of TiO2 nanoparticles in Ni–B bath, which is a recently invented technique, significantly improves the scratch response of the composite coating and its abrasive wear resistance. Indeed, the composite coating appears exempt from delamination after both scratch tests and pin-on-disk test, contrary to the pure Ni–B coating. Regarding the impact wear resistance, it was found that the wear severity and damage mechanisms depend strongly on the impact angle, which in turn is controlled by the solicitation type. The SEM observations accompanied with EDS analysis were carried out inside the wear scars to clearly understand the relationship between the surface damage and the contact angle

On the tribocorrosion behavior of 304L stainless steel in olive pomace/tap water filtrate

International audienceTribocorrosion is a concern in the operation of centrifuges used in olive oil separation from seeds. An investigation was conducted on the tribocorrosion behavior of AISI 304L stainless steel, a typical centrifuge material, sliding against alumina in a mixture of olive pomace and tap water filtrate. A specially-configured pin-on-disc tribometer was used to couple electrochemical analyses with wear tests. The active and passive surface states involved in the tribocorrosion mechanisms for the steel are discussed. Mechanical and corrosion contributions to wear, which acted on the active and repassivated areas of the wear track, were quantified. Abrasive wear dominated in the AISI 304L. It was also found that the steel was more sensitive to tribocorrosion under intermittent sliding than continuous slidin

Thermophysical and Radiative Properties of Conductive Biopolymer Composite

International audienceUsual plate solar collectors, based on a metal absorber (Cu, Al) selectively coated are technologically very sophisticated, expensive to produce and they are great consumer of fossil raw material. Polymeric materials are considered as a promising alternative for many interesting properties; easy moldability, corrosion resistance, they also offer a significant cost-reduction for solar thermal collectors, and a mass production may thus benefit to a broader utilization of solar energy. Most drawbacks of polymers are their low thermal properties; essentially thermal conductivity coefficient may strongly affect the solar absorber efficiency and deteriorate the collector performance. Polymers used in solar collectors are mainly petroleum-derivative product and mass use of them is not a response to environmental concern. That is why the laboratory chose to explore the potentialities of bio-polymers for the production of absorbers. This group of material presents the same properties as ordinary polymers. It is on the other hand possible to modify the thermal properties of the basic matrix by the addition of loads, such as carbon black, graphite or carbon nanotubes. The thermal performance of a solar collector is closely related to the thermal properties of the absorber. Within this framework, many measurements are necessary, more particularly the conductivity, but also emissivity and absorptivity to solar radiation. The aim of this paper is to study the thermal properties of the PLA bio-polymer charged of exfoliated graphite and/or CNT. Thereafter, the total hemispherical absorptivity, an estimation of the total hemispherical emissivity and the thermal conductivity coefficient were measured for different load rates, we will conclude on the interest and the potentialities of tested materials

Elaboration of polymer composite for thermal solar absorber

Colloque Sustainable Chemitry & Related Areas, 25, 26 février 2010 Communication par affich

Thermo-electrical power of a carbon filled Conductive bio-Polymer Composites for electrical energy generation

5th International Conference on Advances in Mechanical Engineering and Mechanics, ICAMEM2010, 18-20 December, 2010, Hammamet, Tunisi

Éco-composites polymères conducteurs (CPC) pour la production d'énergie renouvelable

L augmentation incessante de la consommation mondiale des énergies fossiles risque de plonger notre planète dans une pénurie de ressources énergétiques dans quelques dizaines d années. Les énergies renouvelables semblent être une excellente alternative pour la production d une énergie durable et verte. L objectif de ce travail est d élaborer des Composites Polymères Conducteurs (CPC) pour la production et le stockage d énergie. Dans une première partie, nous nous sommes intéressés au développement d un absorbeur solaire à base de CPC préparés à l état fondu en dispersant une charge conductrice (graphite et/ou nanotubes de carbone) dans une matrice polymère isolante (PLA et PA12). Leurs propriétés thermo-optiques ont été mesurées et une étude de leur durabilité a été réalisée. Dans une seconde partie, des CPC possédant un pouvoir thermoélectrique ont été préparés par voie fondue et solvant par polymérisation in situ. Diverses formulations ont été testées et des facteurs de mérite ZT très encourageant ont été obtenus.Owing to the finite supply of fossil fuels and the negative public opinion surrounding nuclear energy, alternative energy resources are the subject of considerable research on a global scale. The aim of this work is to develop a Conductive Polymer Composite for energy harvesting and storage. The first part of this work was dedicated to the development of solar absorber. In fact, CPCs were prepared by melt processing where conductive fillers (graphite and/or carbon nanotubes) were dispersed in an insulate polymer matrix (PLA and PA12). Indeed, thermo-optical properties were measured and the durability of the CPC was checked by controlling the evolution of their mechanical properties during a weathering test. In a second step, CPC with good thermoelectric power were prepared using two routes: melt blending process and solution in-situ polymerization. Various formulations have been tried and some rather interesting results were obtained by recording encouraging values of figure of merit ZT.LORIENT-BU (561212106) / SudocSudocFranceF

Elaboration of polymer composite for thermal solar absorber

Colloque Sustainable Chemitry & Related Areas, 25, 26 février 2010 Communication par affich