Experimental studies on cement paste exposed to external sulfate attack (ESA), delayed ettringite formation (DEF), and the coupling effect of both reactions are presented in this paper. The objective ...is to compare the degraded state of specimens, the length and mass variations, and the pore size distribution (PSD) obtained by mercury intrusion porosimetry (MIP) of cement paste submitted to these different exposure conditions. By comparing the PSD of specimens before and after the sulfate attacks, a global expansion mechanism is proposed: ettringite first precipitates in the biggest pores without inducing obvious expansion, and then penetrates into capillary and gel pores leading to an accelerated swelling. In addition, the coupling effect of ESA and DEF is found to be the most damaging expansion, which raises a high durability problem for cement-based materials.
Comparativement à d’autres mécanismes de dégradation tels la carbonatation ou la diffusion d’ions chlorures, le gonflement par réaction sulfatique interne (RSI) reste encore un mécanisme très peu ...étudié. Le champ d’investigation reste donc très large et de nombreux verrous scientifiques restent encore ouverts notamment dans les bétons formulés avec additions minérales telles que les cendres volantes, le métakaolin et la pouzzolane. L’objectif de ce travail de thèse est d’apporter de nouveaux éléments pour la compréhension des effets des additions sur la RSI en mélange binaire et ternaire. Tout d’abord, en mélange binaire, il a été montré que l’ettringite est plus présente dans les mortiers que dans les bétons. Pour les mélanges ternaires, nous avons montré que la présence de filler calcaire permet de se combiner à l’aluminate de calcium ce qui favorise la formation du (hémi/mono) carbonate. Le filler réduit ainsi la formation de monosulfoaluminate, ce qui va stabiliser la formation d’ettringite et ainsi diminuer à plus long terme la DEF (Delayed ettringite formation). Quant à l’influence du type d’addition sur la RSI, la présence de sulfate dans l’addition est un facteur déterminant visà- vis de cette pathologie notamment dans le cas des Pouzzolanes et Metakaolins contrairement aux Cendres volantes. Cette étude a permis également de montrer que la quantité d’ettringite différée a tendance à augmenter avec l’augmentation des sollicitations mécaniques en compression par contre la période de déclenchement de RSI reste peu sensible à l’endommagement mécanique.
Compared to other degradation mechanisms such as carbonation or chloride ion diffusion, swelling by internal sulfate attack (ISA) is still a little-studied mechanism. The field of investigation and remains very large and many scientific obstacles are waiting answers especially in concretes with mineral admixtures such as fly ash, metakaolin and natural pozzolan. The objective of this thesis is to bring new elements to understand the effects of the mineral admixtures on the ISA in binary and ternary mixtures. First, in binary mixtures it was shown that ettringite is more present in mortars than in concrete. For the ternary mixtures, we have shown that the presence of limestone filler makes it possible for it to be combined with the calcium aluminates which favors the formation of (hemi / mono) carbonates. The filler reduces monosulfoaluminate formation, which will stabilize the ettringite and thus reduce longer-term delayed ettringite formation (DEF). As for the influence of the type of addition to the ISR, the presence of sulfate in addition is a dominant factor in this pathology particularly in the case of natural pozzolan and metakaolin contrary to the fly ash. This study also showed that the amount of deferred ettringite tends to increase with increasing compressive mechanical stress while the ISA trigger period remains insensitive to mechanical damage. L’Université
Non-benzenoid non-alternant nanographenes (NGs) have attracted increasing attention on account of their distinct electronic and structural features in comparison to their isomeric benzenoid ...counterparts. In this work, we present a series of unprecedented azulene-embedded NGs on Au(111) during the attempted synthesis of cycloheptadeffluorene-based high-spin non-Kekulé structure. Comprehensive scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) evidence the structures and conformations of these unexpected products. The dynamics of the precursor bearing 9-(2,6-dimethylphenyl)anthracene and dihydro-dibenzo-cycloheptadeffluorene units and its reaction products on the surface are analyzed by density functional theory (DFT) and molecular dynamics (MD) simulations. Our study sheds light on the fundamental understanding of precursor design for the fabrication of π-extended non-benzenoid NGs on a metal surface.
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•DC electric field (DEF) (0–30 V) was used to optimize Bovine Serum albumin-Gold nanoparticle (BSA-GNP) corona.•Multilayer adsorption of BSA on GNP was achieved using ...DEF.•Spectroscopic analysis indicates strong binding between DEF (5 V and 15 V) engineered BSA-GNP conjugate and curcumin (CUR).•DEF engineered BSA-GNP conjugate were biocompatible.
Targeted drug delivery (TDD) is a method of delivering optimum concentrations of pharmaceutical substances in the tissue to achieve the desired therapeutic effect. Hence, TDD systems are considered as an emerging strategy to deliver the drug at the specific site of the tissues/cells. The nanoparticle-protein corona as a drug delivery vehicle has demonstrated immense benefits including potential theragnostic, improved pharmacodynamics and targeted drug delivery. In the present investigation, efforts have been to establish stable and functionalized Bovine serum albumin–gold nanoparticle (BSA-GNP) corona (conjugates) using a Direct Current (DC) electric field. With the application of DC electric field (DEF) across the BSA-GNP solution, the formation of BSA-GNP corona/conjugate takes place which was characterized using various biophysical techniques such a Dynamic Light Scattering (DLS), UV Visible spectroscopy, Fluorescence spectroscopy, electrophoresis, etc. Furthermore, the DEF engineered BSA-GNP corona was loaded/interacted with curcumin (CUR). The size of the BSA-GNP corona was increased with increasing DC voltage (5–30 V) at constant concentration of BSA. The strong and stable binding of curcumin with BSA-GNP corona was revealed by the techniques used in the investigation; however, binding affinity of CUR was decreased for 30 V DEF exposed BSA-GNP conjugate. The biocompatible experimental data confirms the nontoxic nature of BSA-GNP corona. This investigation adds a new and novel physical method for the preparation of protein-nanoparticle corona for various applications including drug delivery.
The use of partially filled high porosity graded aluminum and copper foams is explored to satisfy both heat transfer and pressure drop in a heat exchanger. Both positive and negative orientations are ...accomplished for the enhancement of heat transfer with reduction in the pressure drop. The present research includes three different configurations M1, M2 and M3 (porous layer inner diameter = 0.06 m, 0.04 m, and 0.02 m, respectively, while outer diameter = 0.10 m) partially filled with positive (i.e., increasing, 20/45 PPI) negative (i.e., decreasing, 45/20 PPI) and compound (i.e., 45 Cu/20 Al PPI) graded porous layer thickness. Each configuration involves three different graded porous layer to present the optimum graded porous layer thickness. The thermo-hydrodynamic characteristics are apprehended by using Darcy Extended Forchheimer (DEF) flow and local thermal non-equilibrium (LTNE) models for the partially filled graded porous structure and k-ω turbulence model is accomplished in open passage flow of the conduit. The decreasing graded foam located inside the models M1 and M2 performed 1.68%–12.85% and 13.42%–23.32% higher heat transfer rate compared to without graded metal foam of models M2 and M3, respectively accompanied with 55.43%–84.02% and 35.69%–50.31% lesser pumping power.
•Partially filled negative graded metal foam is suggested for heat transfer enhancement.•The negative graded foam was found superior than the positive graded foam layer.•The thinnest negative graded foam layer displayed maximum thermal performance.•The negative graded copper foam shows slightly higher performance than aluminium one.
4H‐Cyclopentadefphenanthrene (CPP) is a valuable building block in the production of photoactive polymers, which find use in a wide range of organic electronic applications. Of particular importance ...is their use in the development of blue‐colored, organic light‐emitting diodes (OLEDs), which remains a challenge in the field. Unfortunately, commercial sources and synthetic procedures known in the literature are unable to provide enough CPP for large scale implementation. Herein, we report on the development of a novel, gram‐scale synthesis of CPP in three steps, starting from pyrene. The key steps in our methodology are the ring contraction of pyrene‐4,5‐dione to oxoCPP in a single step, as well as the direct reduction of oxoCPP to CPP. Apart from the small number of synthetic steps, our methodology benefits from the use of relatively non‐hazardous reagents, together with optimized purification procedures, making CPP accessible in useful quantities.
CPP is a valuable building block in the production of photoactive materials. A short and economical synthesis route to this material is thus much desired. We here report a three‐step procedure, starting from pyrene, which allows access to this material on a gram scale. Our route is characterized by the use of relatively non‐hazardous materials and fully optimized purification protocols.
•The evolution of global phase assemblage after a delayed heat treatment (<80 °C) on 3 cement pastes (CEM I, CEM II/A and CEM V/A with fly ash and slag)•Partial reversible effect after ...re-immersion.•The probability of DEF occurrence.
This paper focuses on studying the effect of the delayed heating of cementitious materials on the phase assemblage variations in three types of cement paste. Two heating temperatures of the order of 65 °C and 80 °C were used to thermal treat the samples. Our results show that the thermal treatment induces the modification of the phase assemblage(particularly degradation of AFt and AFm phases) as well as the polymerization of the C-(A)-S-H. The observed variations depend mainly on the initial sulfate, aluminate and carbonate content in each cement. Finally, it is shown that the thermal treatment-related phenomena such as adsorption of aluminates on C-(A)-S-H are almost completely reversible after the temperature drop and re-immersion in water for 3 months, meanwhile other phenomena such as the formation of the hydrogarnet and hydrotalcite are only partially reversible. This modifies the free elements proportion and influences the probability of the DEF occurrence.
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