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31.
Chemical reactivity of mineral aggregates in aqueous solution: relationship with bitumen emulsion breaking 总被引:1,自引:1,他引:0
Layella Ziyani Vincent Gaudefroy Valéry Ferber Dimitri Deneele Ferhat Hammoum 《Journal of Materials Science》2014,49(6):2465-2476
This paper reports a study on chemical reactivity of gneiss, diorite and limestone aggregates in aqueous solution. The originality of this study is that it extended to very short times (less than 1440 min). Rise in pH tests was implemented and dissolution kinetics was analysed. The results showed that calcium was the major element released by the aggregates. It has also been found that dissolution had an influence on the final morphology of aggregates. Polyamine emulsifier adsorption onto aggregates has been assessed using electrophoresis. Finally, the rise in pH and electrophoretic tests were compared to the breaking test traditionally performed to characterise bitumen emulsions. It was found that breaking values were controlled by both the surface area and the surface charge of the particles. Results may be correlated to polyamine adsorption on aggregates. Adsorption seemed to be efficient for gneiss and diorite: at pH 2, their charge turned from slightly negative to highly positive. At this pH value, limestone particles were dissolved and polyamine adsorption must be less efficient than with gneiss and diorite, for which the emulsion breaking was facilitated by the high attraction of particles for the emulsifier, due to their negative surface charge. 相似文献
32.
Val rie Eychenne Zphirin Mouloungui 《Journal of the American Oil Chemists' Society》2001,78(3):229-234
Thionation using the Lawesson’s reagent (LR) led to quantitative and selective replacement of carbonyl groups (C=O) with thionocarbonyl
groups (C=S). Mixtures of thionotriglycerides were obtained by reaction of 2,4-bis (p-methoxyphenyl)-1,3-dithia-2,4-diphosphetane-2,4-disulfide in suspension with triglycerides (TG). With a molar ratio (LR)/(TG)=3∶2,
there was complete exchange of C=O with C=S in the carboxylic groups of the TG. The yield is over 90%. The two P=S ligands
in the LR confer a double reactivity, producing a high power of thionation. Fourier transform infrared spectroscopy was employed
for quantitative and qualitative characterization of the thionated TG and for monitoring the progress of partial or total
thionation as conditioned by the molar ratios of the starting compounds. Thus, with molar ration LR/TG of 0.108, 0.36, and
0.72, we obtained around 6, 20, and 40% of C=O conversion, respectively. 相似文献
33.
George F. Finco Karina G. Fiametti Viviane da Silva Lobo Edson A. da Silva Fernando Palú João H. C. Wancura Maria L. F. Rodrigues Alexsandra Valério José Vladimir de Oliveira 《Journal of the American Oil Chemists' Society》2022,99(7):559-568
Monoacylglycerol (MAG) and diacylglycerol (DAG) are two natural components found in most edible oils and fats. Conventional synthesis of MAG and DAG is usually conducted by glycerolysis of triacylglycerol (TAG) at high temperatures (above 200°C) in the presence of an alkaline catalyst. In this work, the synthesis of MAG and DAG using enzymatic glycerolysis of olive oil was investigated using Tween 80 as surfactant, n-butanol as co-surfactant and the novel lipase in free/liquid formulation Lipozyme TL 100L as catalyst. Experimental design was used to evaluate the effect of enzyme load and reaction temperature on the feedstock conversion. Enzyme load and system temperature were significant variables in the statistical design and the best condition was found at 35°C, 7.5 vol% of Lipozyme TL 100L and glycerol to oil volumetric ratio of 2:1 with conversion of TAG at approximately 98% after 2 h of process. A mathematical model based on the Ping-Pong Bi-Bi mechanism was used to describe the reaction kinetics. The model adequately described the behavior of the system and can be a useful tool for the design of reactors in larger scales. 相似文献
34.
Usually, the time of repair/replacement of reinforced concrete structures due to corrosion is controlled by cracking of the concrete cover. Thus, it is important to be able to predict with sufficient accuracy the time from corrosion initiation to crack formation in the concrete cover. The paper presents a critical overview of existing empirical, analytical and numerical models for predicting the time to corrosion-induced cover cracking. A simple nonlinear finite element (FE) is then formulated and validated. The FE model is employed to investigate inaccuracies of analytical models arising due to simplified formulation of the nonlinear behaviour of concrete and inability to account for actual location of corroding reinforcing bars. Recommendations on the applicability of analytical models are provided. Finally, the FE model is used to estimate the amount of corrosion products penetrating into concrete pores and microcracks since this amount is an essential parameter for analytical and numerical models. 相似文献
35.
A representative and comprehensive review of the electrical and thermal properties of polymer composites with carbon nanotube and other nanoparticle fillers 下载免费PDF全文
Mohammad Jouni David Djurado Valérie Massardier Gisèle Boiteux 《Polymer International》2017,66(9):1237-1251
In this review we present the results of our literature investigation into the electrical and thermal properties of carbon nanotube polymer composites. A short selection of data relating to conductive polymer composites with various fillers is provided for comparison. The effects of filler properties such as type and size, the use of hybrid fillers, fabrication methods for polymer composites and the importance of the modeling of the electronic and thermal transport mechanisms are discussed, as are more general factors influencing the properties of these composites. This review represents a comprehensive survey and constructive study and should serve as a useful reference tool for industrial and academic researchers working in this field. © 2017 Society of Chemical Industry 相似文献
36.
M. Harničárová J. Valíček R. Grznárik H. Tozan P. Koštial M. Kušnerová 《Materialwissenschaft und Werkstofftechnik》2014,45(4):281-285
In recent years, laser cutting has been introduced and developed to such an extent that it is now thought to be one of the leading and indispensable manufacturing tools. At the present time, dross‐free and accurately‐cut parts are basically regarded as the major targets to aim for, because the costs and efforts associated with dross removal by postprocessing cut parts are considerable. Therefore, control of dross formation during laser cutting is an important factor in maintaining edge quality. The initial aim of this paper is to describe the importance of physico‐mechanical material properties that need to be taken into account in modeling of laser material processing in order to control melting of the material. 相似文献
37.
This study addresses heat and mass transfer during the vaporization of a liquid in a heated square cross-section mini-channel. A theoretical model is developed in steady state using the radius of curvature as a variable. One-dimensional simulations have been performed. An analysis of this model reveals that heat and mass transfer is governed by two main groups of non-dimensional numbers (i.e., Reynolds × Boiling and Weber × Boiling2 numbers). Maps of heat transfer performance are thus proposed according to these non-dimensional numbers. A reduced model is finally derived, allowing the main parameters to be expressed (such as the extended meniscus length) analytically. 相似文献
38.
39.
Eunice Valduga Alexsandra Valério Pihetra Oliveira Tatsch Helen Treichel Agenor Furigo Jr. Marco Di Luccio 《Food and Bioprocess Technology》2009,2(2):234-238
The increasing demand for carotenoids by industries has drawn attention to their bio-production. Since pigments are intracellular,
extraction steps are then needed after cell cultivation. In this work, different strategies for extraction of carotenoid pigments
from Sporidiobolus salmonicolor (CBS 2636) were studied. Different solvents (dimethyl sulfoxide, petroleum ether, hexane, ethyl acetate, chloroform, and
acetone), liquid N2, and diatomaceous earth were used to disrupt the cell and thus release the intracellular carotenoids. The results of this
study showed that when multiple solvents were used, a synergistic effect on the extent of carotenoids recovery was obtained.
Maximum concentration of total carotenoids (913 μg/L) was obtained in the treatment using liquid N2 and dimethyl sulfoxide to disrupt the cell, followed by the extraction with a solution of acetone/methanol (7:3, v/v). 相似文献
40.
Summary
The dielectric behaviour through DETA system has been studied for six PVC samples of distinct molecular microstructure in
terms of content and associated surroundings and conformation of the local configurations mmr termini of isotactic sequences. Both the dielectric studies and the microstructure of the samples, as obtained by stereospecific
substitution reaction of an additive-free commercial PVC are to be published in detail separately. For purposes of clarity
some of the results are mentioned in Experimental section.
The phenomenological correlation between the β parameter as defined by Ngai's theory and the microstructure of the samples,
quantities both issued from the above quoted work, is considered in the present paper with the objective of providing some
novel ideas on the physical meaning, at molecular level, of the Ngai's coupling parameter, in the light of mobility constraints
and local free volume associated with mmr structure at its likely conformations.
Received: 16 March 2001/Revised version: 18 June 2001/Accepted: 24 July 2001 相似文献