The (love & hate) role of entropy in process metallurgy / Halvard Tveit in MATERIAUX & TECHNIQUES, Vol. 107, N° 5 (2019)  

[article]  inMATERIAUX & TECHNIQUES > Vol. 107, N° 5 (2019) . - 8 p. Titre : The (love & hate) role of entropy in process metallurgy Type de document : texte imprimé Auteurs : Halvard Tveit, Auteur ; Leiv Kolbeinsen, Auteur Année de publication : 2020 Article en page(s) : 8 p. Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Energie Entropie (thermodynamique) Silicones Les silicones, ou polysiloxanes, sont des composés inorganiques formés d'une chaine silicium-oxygène (...-Si-O-Si-O-Si-O-...) sur laquelle des groupes se fixent, sur les atomes de silicium. Certains groupes organiques peuvent être utilisés pour relier entre elles plusieurs de ces chaines (...-Si-O-...). Le type le plus courant est le poly(diméthylsiloxane) linéaire ou PDMS. Le second groupe en importance de matériaux en silicone est celui des résines de silicone, formées par des oligosiloxanes ramifiés ou en forme de cage (wiki). Index. décimale : 668.9 Polymères Résumé : Process metallurgy is the basis for the production, refining and recycling of metals and is based on knowledge of transport phenomena, thermodynamics and reaction kinetics, and of their interaction in high-temperature, heterogeneous metallurgical processes. The entropy concept is crucial in describing such systems, but, because entropy is not directly observable, some effort is required to grasp the role of entropy in process metallurgy. In this paper, we will give some examples of how entropy has a positive effect on efforts to reach the process objectives in some cases, while in other cases, entropy acts in contradiction to the desired results. In order to do this, it is necessary to have a closer look at both the entropy concept itself as well as at other functions like free energy and exergy since they encompass entropy. The chosen case is the production of silicon. It is the huge entropy change in the process that is utilized. The case is not chosen arbitrary. Indeed, it is the authors’ strong belief that silicon will be one of the foundations for the environmental and energy future planned for in the “Paris-agreement”. We will also explore relatively recent research in physics and thermodynamics that led to the description of the concepts like “dissipative systems and structures”. Dissipative systems are thermodynamically open systems, operating out of, and often far from thermodynamic equilibrium and exhibit dynamical regimes that are in some sense in a reproducible self-organized steady state. Such structures can arise almost everywhere provided this structure, feeding on low entropy resources, dissipates entropy generated in the form of heat and waste material in parallel with the wanted products/results. Examples range from metallurgical processes to the emergence of industrial symbiosis. Note de contenu : - Introduction (based mainly on [1]) - The Paris Agreement - and the consequence for the energy usage - Silicon - the metalloid hero faces new assignments for humanity - The silicon processes - The exergy destruction in silicon production - Some thoughts about silicon production and the future Référence de l'article : 506 DOI : https://doi.org/10.1051/mattech/2019028 En ligne : https://www.mattech-journal.org/articles/mattech/pdf/2019/05/mt190044.pdf Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=34446 [article]

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Theory and mechanism of tanning present thinking and future implications for industry / Anthony D. Covington in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 85, N° 1 (01-02/2001)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 85, N° 1 (01-02/2001) . - p. 24-34 Titre : Theory and mechanism of tanning present thinking and future implications for industry Type de document : texte imprimé Auteurs : Anthony D. Covington, Auteur Année de publication : 2001 Article en page(s) : p. 24-34 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Entropie (thermodynamique) Hydrogène Hydroxyproline Tannage au chrome Tannage organique Température de retrait Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : The range and nature of reactions that contribute to the stability of collagen are discussed in terms of the definition of tanning. Previous ideas of the origin of hydrothermal stability of modified collagen are included in the discussion. A new theory of the origin of hydrothermal stability is defined, based upon the relative contributions of entropic and enthalpic changes to collagen by interactive chemical processes. These changes culminate in stabilisation by the formation of matrices, that are capable of producing high hydrothermal stability. Ts> 100°C. The theory explains the whole range of observed effects in mineral (inorganic) and organic tanning reactions, thereby creating an inclusive, unifying model of collagen stabilisation. Furthermore, it allows not only prediction of the effects of any new tanning processes, mineral or organic, together with modifications to current processes, but also specifies where new chemistries might be sought, to achieve high hydrothermal stability. Note de contenu : - The definition of tanning - The shrinking transition - The roles of hydroxyproline and hydrogen - Entropic effect - The thermodynamics of tanning and shrinking - The shrinking reaction - Organic tanning - Chromium(III) tanning - Completing the theory of tanning - Future developments - Table 1 : The rise in shrinkage temperature caused by traditional tannages - Table 2 : Typical shrinkage temperatures for leathers tanned with modern chemistries - Table 3 : The dependence of shrinkage temperature on imino acid content of collagens - Table 4 : The effect of polypeptide structure on the unfolding transition temperature - Table 5 : The effects of sodium salts on collagen - Table 6 : The effect of fluoride ion on collagen stabilisation - Table 7 : Activation parameters at 333 K for different tannages (adapted from ref. 26) - Table 8 : The relationship between shrinkage temperature and the parameters of the shrinking reaction - Table 9 : The size of the cooperating unit in unmodified and modified collagen - Table 10 : The maximum effect of excess carboxylate on the shrinkage temperature of leather tanned with 40 % basic chromium(lhl) perchhorate - Table 11 : Apparent shrinkage temperature of hide powder equilibrated with alcohol En ligne : https://drive.google.com/file/d/1VSARpzkIMKqpj_JryvcFwaZ5TJft8nZ5/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=40591 [article]

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Thermodynamics of leather dyeing : III. The preparation of chrome-tanned hide powders and their interaction with C.I. Acid Orange 7 / A. T. Atto in JOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS, Vol. 55, N° 3 (03/1971)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS > Vol. 55, N° 3 (03/1971) . - p. 84-103 Titre : Thermodynamics of leather dyeing : III. The preparation of chrome-tanned hide powders and their interaction with C.I. Acid Orange 7 Type de document : texte imprimé Auteurs : A. T. Atto, Auteur ; H. E. Nursten, Auteur Année de publication : 1971 Article en page(s) : p. 84-103 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Colorants acides Cuirs et peaux -- Teinture Entropie (thermodynamique) Orange (couleur) Poudre de peaux Tannage au chrome Thermodynamique Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : A procedure has been developed for chrome-tanning hide powder and it has been used to prepare a range of chrome-tanned hide powders with increasing chrome contents. The interaction of these tanned hide powders with the pure dye acid of C.I. Acid Orange 7 has been studied thermo-dynamically. The saturation capacity of the tanned hide powder for the acid dye increases almost linearly with the amount of chromium present, a chrome oxide content of about 3 % leading to a saturation capacity about twice that of untanned hide powder. The saturation capacities can be sur¬prisingly large, rising to almost three molecules dye bound per chromium atom. Chrome-tanned hide powder has been found to have a lower affinity for the acid dye than untanned, which is connected with the much larger satura¬tion capacity and the consequently lower activity in the fibre produced by a given amount of dye on the hide powder. The affinity at 60°c is independent of minor differences in tannage, but decreases with increasing amounts of chromium. The affinity increases with temperature in the range 25-75°c, while the saturation capacity decreases. Ageing chrome-tanned hide powder does not affect the affinity, but decreases somewhat the saturation capacity. Dyeing chrome-tanned hide powder appears to be exothermic and the entropies of dyeing are positive, the process thus being thermodynamically similar to dyeing untanned hide powder. Note de contenu : - Preparation of a number of batches of chrome-tanned hide powder (A) C20 hide powder - (B) ATA hide powder, Batch 1 - (C) ATA Hide powder, Batch 2 - (D) ATA hide powder (relatively very low chrome content) batch 3a - (E) ATA hide powder (relatively High chrome content), Batch 3b - Analysis of the tanned hide powders - Purification and analysis of the dye used - Dyeing - Reversibility of dyeing - Table 1 : Analysis of the tanned hide powders - Table 2 : Experimental data and quantities calculated therefrom - Table 3 : Saturation capacities of some chrome-tanned hide powders for C.I. Acid Orange 7 - Table 4 : Affinity of C.I. Acid Orange 7 for some chrome-tanned hide powders - Table 5 : Variation of affinity of C.I. Acid Orange 7 for chrome-tanned hide powder with chrome content - Table 6 : Comparison of the activity of C.I. Acid Orange 7 in tanned and untanned hide powder - Table 7 : Heats and entropies of dyeing of some chrome-tanned hide powders with C.I. Acid Orange 7 Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35668 [article]

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Thermodynamics of leather dyeing / A. T. Atto in JOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS, Vol. 55, N° 5 (05/1971)

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TRADES' CHEMISTS > Vol. 55, N° 5 (05/1971) . - p. 163-174 Titre : Thermodynamics of leather dyeing : IV. Dyeing of chrome-tanned hide powder with simple acid dyes Type de document : texte imprimé Auteurs : A. T. Atto, Auteur ; H. E. Nursten, Auteur Année de publication : 1971 Article en page(s) : p. 163-174 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Colorants acides Cuirs et peaux -- Teinture Entropie (thermodynamique) Poudre de peaux Tannage au chrome Titrage thermométrique Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : The previous study of the interaction between chrome-tanned hide powder and C.I. Acid Orange 7 has been extended to seven other simple acid dyes in the form of their specially purified dye acids. Good reciprocal plots were obtained at 45 and 60°c, leading to saturation capacities greater than 2 meq/g dry hide substance, except for the dye acids bearing sulphonic groups peri to the azo link. The affinities obtained are lower than those for untanned hide powder and this must be viewed as a consequence of the much greater saturation capacity, which leads to the production of a lower activity in the fibre by a given amount of dye. The affinity of a dye acid for chrome-tanned hide powder increases with the insertion of a methyl group or a fused-on benzene ring, but movement of a sulphonic group to a position peri to the azo link reduces it. Overall, the standard heats and entropies of dyeing chrome-tanned hide powder are of the same sign and order of magnitude as those for the untanned substrate. The thermodynamics of dyeing chrome-tanned hide powder thus do not appear to differ fundamentally from those of dyeing untanned hide powder. Note de contenu : - EXPERIMENTAL : The dyes - Substrates - Dyeing - RESULTS AND DISCUSSION : The reciprocal plot - Titration curves - Saturation capacities - Affinities - Heats of dyeing - Entropies of dyeing - Table 1 : Experimental data and quantities calculated therefrom - Table 2 : Saturation capacities, affinities and ratio dye acid/Cr atom of chrome-tanned ATA 1114e powder for a range of simple dye acids - Table 3 : Affinities of some simple dye acids for untanned and tanned hide powder kcal/mole - Table 4 : Heats and entropies of dyeing chrome-tanned hide powder with some simple dye acids at 45-60 °C Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=35667 [article]

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