Nouveaux gisements fossilifères à Charophytes barrémiens dans les "Grès du Liban" auct. (Liban), avec un point de vue critique sur la nature de Munieria Deecke, 1883

The "Grès du Liban" auct. is the thick basal unit of the Lower Cretaceous series in Lebanon. There are two key levels in this dominantly siliciclastic unit: the "Banc de Mréjatt" and the "Calcaire à pisolithes", the latter of which includes limestones and marls with Charophyta. The rich charophyte assemblage described by Grambast and Lorch (1968) from a site near Jezzine is Barremian (possibly Early Barremian) in age, not Bedoulian as previously stated. Besides gyrogonites and utricles, charophyte thalli are rather common; they are ascribed to two organ genera, Munieria Deecke, 1883, and Charaxis Harris, 1939. Based on topotypic material (from the Pia Collection), Munieria baconica Deecke, 1883, the type-species of the genus, is reassessed. In addition, the species Clypeina parvula Carozzi, 1946, is transferred to the revised genus Munieria, and a new species of Charaxis is described.Les "Grès du Liban" auct. constituent l'épaisse unité à la base des séries du Crétacé inférieur au Liban. Il y a deux niveaux-repères dans cette unité essentiellement silicoclastique : le "Banc de Mréjatt" et le "Calcaire à pisolithes" ; ce dernier comporte des passées calcaires ou marneuses à Charophytes. La riche association de Charophytes décrite par Grambast et Lorch (1968) comme provenant d'un site proche de Jezzine est d'âge barrémien (peut-être Barrémien inférieur) et non bédoulien comme cela était indiqué précédemment. À côté des gyrogonites et des utricules, les thalles de Charophytes sont plutôt communs ; ils sont attribués à deux genres d'organes, Munieria Deecke, 1883, et Charaxis Harris, 1939. Sur la base de matériel topotypique (provenant de la Collection Pia), Munieria baconica Deecke, 1883, l'espèce-type du genre, est réexaminée. Pour compléter cette étude, nous transférons l'espèce Clypeina parvula Carozzi, 1946, dans le genre Munieria révisé et décrivons une nouvelle espèce du genre Charaxis

The effect of ALD oxides thin films on the electrochemical properties of the sputtered Al-Zr coatings

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Evaluation of the Effect of Different Types of Abrasive Surface Treatment before and after Zirconia Sintering on Its Structural Composition and Bond Strength with Resin Cement

This study evaluated the effect of air abrasion before and after sintering with different particle type, shape, and size on the surface morphology, monoclinic phase transformation, and bond strength between resin cement and zirconia surface using primer containing silane and MDP. Airborne particle abrasion (APA) was performed on zirconia before and after sintering with different particle shape and size (50 μm Al2O3 and 25 μm silica powder). 120 square shaped presintered zirconia samples (Amann Girrbach) were prepared (3 mm height × 10 mm width × 10 mm length) and polished with grit papers #800, 1000, 1200, 1500, and 2000. Samples were divided into 6 groups according to surface treatment—group A: (control) no surface treatment; group B: APA 50 μm Al2O3 before sintering (BS); group C: APA 50 μm Al2O3 after sintering (AS); group D: APA25 μm silica powder (BS); group E: APA25 μm silica powder (AS) at a pressure of 3.5 bar; and group F: APA 25 μm silica powder (AS) at a pressure of 4 bar. Samples were analyzed using XRD, AFM, and SEM. The samples were submitted to shear bond strength (SBS) test. A dual cure resin cement (RelyX Ultimate) and primer (Scotchbond Universal) were used. Data were analyzed with ANOVA and Tukey test (α≥0.05). APA in group B significantly increased the surface roughness when compared to all other groups. A significant monoclinic phase transformation (t-m) value was observed in groups C and F and a reverse transformation occurred in presintered groups. The SBS value of group A was 11.58±1.43 and the highest significant shear bond strength value was for groups B (15.86±1.92) and C (17.59±2.21 MPa) with no significant difference between them. Conclusions. The use of APA 50 μm Al2O3 before sintering and the application of primer containing MDP seem to be valuable methods for durable bonding with zirconia. The use of APA 50 μm Al2O3 after sintering induced the highest (t-m) phase transformation

Friction reduction in elastohydrodynamic contacts by thin-layer thermal insulation

Reducing friction is of utmost importance to improve efficiency and lifetime of many products used in our daily lives. Thin hard coatings like diamond-like carbon (DLC) have been shown to reduce friction in full-film-lubricated contacts. In this work, it is shown that contrarily to common belief, the friction reduction stems mainly from a thermal phenomenon and not only a chemical/surface interaction one. It is shown that a few micrometer-thin DLC coating can significantly influence the thermal behavior in a lubricated mechanical system. The presented simulations, validated by experiments, show that applying a thin DLC coating to metal surfaces creates an insulating effect that due to the increased liquid lubricant film temperature at the center of the contact, locally reduces lubricant viscosity and thus friction. The results of the investigation show that the addition of thin insulating layers could lead to substantial performance increases in many applications. On a component level, the contact friction coefficient in some common machine components like gears, rolling element bearings, and cam followers can potentially be reduced by more than 40 %. This will most likely open up the way to new families of coatings with a focus on thermal properties that may be both cheaper and more suitable in certain applications than DLC coatingsGodkänd; 2014; Bibliografisk uppgift: Nature | Research Highlights Warm carbon coat reduces friction Nature 505, 264 Published online 15 January 2014 "A coating material made of carbon reduces friction not just by providing a slippery surface, but also by keeping the points of contact warm. Marcus Björling of Luleå University of Technology in Sweden and his team coated steel balls with 'diamond-like carbon' — a material in which the carbon atoms have a bonding pattern similar to that of diamond. They rolled the balls against a metal disk with an oil lubricant in between, and showed that the carbon coating acts as an insulator, lowering the viscosity of the lubricant and thus reducing the friction between the ball and the disk. The findings could encourage the development of lubricant coatings made from insulating materials."; 20140113 (andbra)</p

Design of Multilayers of Urchin-like ZnO Nanowires Coated with TiO 2 Nanostructures for Dye-Sensitized Solar Cells

International audienceIn dye-sensitized solar cells, the photovoltaic efficiency of nanowires (NW) is still limited by their surface area and loss of light absorption compared with nanoparticle (NP) architectures. To overcome this limitation, the light harvesting efficiencies must be improved by increasing the total NW array surface area, without increasing too much the traveled distance of electrons. Here, we describe the design of a 3D architecture based on polystyrene spheres (PS) coated with ordered multilayers of urchin-like ZnO NWs (U-ZnO NWs) to be used as a high surface area nanostructure photoanode for dye-sensitized solar cells. Two to four layers of U-ZnO NWs were synthesized by using PS of 1 and 5 mu m in diameter. The ordered layers of U-ZnO NWs were then coated with a thin layer of TiO2 by atomic layer deposition, and topped with a similar to 9-14 mu m thick layer of anatase TiO2 NPs. We found that assembling organized layers of U-ZnO NWs significantly increased the surface area and provided better photon absorption. Moreover, coating the U-ZnO NWs with a thin TiO2 layer decreased the charge recombination and consequently enhanced the photovoltaic efficiency

Effect of Al₂O₃, ZnO and TiO₂ Atomic Layer Deposition Grown Thin Films on the Electrochemical and Mechanical Properties of Sputtered Al-Zr Coating

The 316L stainless steels, often used in turbine blades for naval and marine applications, usually suffer from localized pitting corrosion after long exposure to chlorinated environments. The aluminum-zirconium coatings deposited by magnetron sputtering technique can be used to ensure cathodic protection for steels. In this work, we study the influence of atomic layer deposited (ALD) Al2O3, ZnO, and TiO2 thin films on the structural, mechanical, and electrochemical properties of Al-Zr (4 at.% Zr) magnetron sputtered coatings. The morphology, preferred orientation growth, mechanical properties, wettability, and corrosion resistance were investigated. The change in the sputtered Al-Zr morphology is mainly due to the insertion of the ALD layer. The Al-Zr layer deposited on ZnO and TiO2 layers presented a distinctive morphology. The agglomerate particles of AlZr/Al2O3/AlZr, AlZr/ZnO/AlZr and AlZr/TiO2/AlZr coatings exhibited a cauliflower shape. For ALD/PVD coatings, the insertion of an ALD oxide layer promoted the intensity of the peaks corresponding to the (111) crystallographic orientation. The nanoindentation measurements confirmed the enhancement in the mechanical properties, where the hardness increased by about 75%. The ALD oxide layers promoted the hydrophobicity of the coatings. The electrochemical characterization in a 3.5 wt.% NaCl solution also confirmed the role of the ALD oxides layers in delaying the pitting corrosion of the Al-Zr coating by widening the passive region and enhancing the protective efficiency of the passive film

A review on the current research on graphene-based aerogels and their applications

Graphene aerogels (GAs) are amongst the lightest materials in the world. They attracted increasing interest in academia and industry because of their exceptional and unique properties, like high mechanical strength, electrical conductivity, thermal resistance, and adsorption capacity. In this review, we describe advances in research and development of a variety of methods that lead to the synthesis of graphene-based aerogels. First, the main common methods for producing GAs are examined, such as chemical reduction, hydrothermal reduction, crosslinking, polymerization methods, and template-directed reduction. Furthermore, the advancement of the 3D printing of GAs is presented. These methods resulted in GAs with porous hierarchical textures, low densities, and improved electrical conductivities, robust mechanical properties, better stability, and excellent adsorption potential. Then, the promising potential applications of GAs in the domains of energy storage, energy conversion, and environmental protection are evaluated. Finally, the prospects and challenges associated with the manufacturing of GAs are discussed

Towards the true prediction of EHL friction

The capability to predict elastohydrodynamic film-thickness and friction from primary measurements of transport properties of liquid has been an elusive goal for tribologists for 50 years. Most comparisons between predictions and experiments involve some amount of tuning of the model in order to match the experimental results. In true prediction, this cannot be done since there are normally no experimental results to compare to. Primary measurements of lubricant transport properties of Squalane were performed, and used in a numerical friction prediction model. Afterwards, friction was measured in a ball-on-disc tribotester. No tuning of the lubricant properties, model or test setup were applied. The current work on EHL-friction is therefore a true representation of the current level of EHL-friction prediction.Validerad; 2013; 20130422 (andbra)</p

Comparative Analysis of Nitrides Band Structures Calculated by the Empirical Pseudopotential Method

International audienceThe electronic band structures of zinc blende and wurtzite GaN and InN are calculated using the empirical pseudopotential method, with the form factors adjusted to reproduce correctly the most important band features. To this end, a comprehensive analysis and comparison with several experimental and theoretical data reported in the literature is performed. Relevant energy spacings as well as direct and indirect band gaps are then derived from the band structures. The electron effective masses at high symmetry points are also obtained using a parabolic line fit. The calculated parameters are reported together with existing data so that they can be easily compared and used in the interpretation of experiments and for numerical simulation purposes

Stabilization and encapsulation of magnetite nanoparticles

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