Bibliographies thématiques / Chromide

Littérature scientifique sur le sujet « Chromide »

Auteur : Grafiati

Publié le 25 mai 2024

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Articles de revues sur le sujet "Chromide"

Scheer, M., et P. G. Jones. « Bis(triphenylphosphine-P)iminium Trichloro(η5-cyclopentadienyl)chromide(III) ». Acta Crystallographica Section C Crystal Structure Communications 53, n^o 8 (15 août 1997) : 1038–39. http://dx.doi.org/10.1107/s0108270197005234.

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Armstrong, RD, et HW Ferguson. « Systemic viral disease of the chromide cichlid Etroplus maculates ». Diseases of Aquatic Organisms 7 (1989) : 155–57. http://dx.doi.org/10.3354/dao007155.

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Jithendran, K. P., A. Navaneeth Krishnan, P. T. Aneesh, P. Ezhil Praveena et T. Bhuvaneswari. « Susceptibility of orange chromide, Etroplus maculatus (Bloch, 1795) to experimental infection of Betanodavirus ». Aquaculture International 29, n^o 2 (22 janvier 2021) : 697–710. http://dx.doi.org/10.1007/s10499-021-00648-y.

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Butvina, V. G., S. S. Vorobey, O. G. Safonov, D. A. Varlamov, G. V. Bondarenko et Yu B. Shapovalov. « Experimental study of formation of chromian priderite and yimengite as products of modal mantle metasomatism ». Доклады Академии наук 486, n^o 6 (28 juin 2019) : 709–13. http://dx.doi.org/10.31857/s0869-56524866709-713.

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The article presents the data of a series of experiments on the synthesis of exotic titanates (priderite and yimengite) as a result of the reproduction of metasomatic conditions of transformation of mantle minerals (chromite, ilmenite). It was first synthesized chromian priderite not containing Ba. The experiments showed the possibility of crystallization of this mineral as a reaction product of high-chromium spinel and rutile with potassium aqueous carbonate fluid (melt) in the upper mantle. In particular, the obtained experimental data allow us to interpret the relationship between K-Cr-priderite and carbonate-silicate inclusions in chromites of Bohemian garnet peridotites. In the experimental study of the reaction of chromite and ilmenite with aqueous potassium-carbonate fluid (melt) obtained both phases of titanates (priderite and yimengite) - indicator minerals, mantle metasomatism, which directly confirms the possibility of formation of yimengite and K-Cr-priderite and other titanates, the result of mantle metasomatism of upper mantle peridotite under conditions of the highest activity of potassium.

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Ostrander, Gary K., et Jack A. Ward. « The function of the pelvic fins during courtship and spawning in the orange chromide, Etroplus maculatus ». Environmental Biology of Fishes 13, n^o 3 (juillet 1985) : 203–10. http://dx.doi.org/10.1007/bf00000932.

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Escudero-Castejon, Lidia, Sergio Sanchez-Segado, Stephen Parirenyatwa et Animesh Jha. « Formation of Chromium-Containing Molten Salt Phase during Roasting of Chromite Ore with Sodium and Potassium Hydroxides ». Journal for Manufacturing Science and Production 16, n^o 4 (1 décembre 2016) : 215–25. http://dx.doi.org/10.1515/jmsp-2016-0023.

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AbstractChromium has a wide range of applications including metals and alloys manufacturing, pigments, corrosion resistance coatings and leather tanning. The production of chromium chemicals is based on the oxidative alkali roasting of chromite ores, which leads to the formation of water-soluble alkali chromates. Previous investigations reported that when chromite is roasted with soda-ash, a molten salt containing chromium, which is mainly composed of sodium carbonate and sodium chromate (Na2CO3-Na2CrO4 binary mixture), forms under typical roasting conditions. The physical properties of the liquid phase, which are dependent on the temperature, charge and gangue compositions, play an important role on the oxidation reaction and may limit the chromate recovery by hindering the oxygen transport to the reaction interface. This investigation focuses on the alkali roasting of chromite ore at 1,000 oC using NaOH and KOH, followed by water leaching. The influence of the alkali ratio on the chromium extraction yield is analysed, and the results obtained with both hydroxides are compared. Sample characterisation and thermodynamic analysis, including phase diagrams, equilibrium calculations and computation of liquidus curves, are combined with the purpose of studying the formation of the molten salt phase under different roasting conditions and its effect on the final chromium recovery.

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Lalomov, Alexander V., Ildar R. Rakhimov et Antonina V. Grigor’eva. « Chromite placer occurrences of the Volga-Ural basin – genesis, sources and industrial potential ». Georesursy 23, n^o 3 (30 août 2021) : 143–48. http://dx.doi.org/10.18599/grs.2021.3.17.

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Chromium is a strategic metal, but more than a half of Russia’s needs are met by imports, so new deposits of chromites, including unconventional placer deposits, are of industrial and scientific interest. Previous studies and current works of the authors of the article have established the chromite placer metal content of Permian-Jurassic deposits of the Volga-Ural basin, which has industrial and potential significance: within the Lukoyanovsky placer area (Nizhny Novgorod region), the industrial chromite content of Jurassic coastal-marine titanium-zirconium placers has been established; in the south-west of Bashkiria, chromite-bearing sands (Sabantuy occurrence) with increased contents, but not yet clear industrial potential. The study of the typomorphism of chromites indicate their close relationship with the chrome spinel of ophiolite associations. The assumed overthrust structure of chromite-bearing hyperbasites of the Urals suggests a wide distribution of chromite-bearing sands within the Upper Permian-Jurassic Volga-Ural paleobasin, in which the increased content of chromites was controlled by hydro- and lithodynamic conditions favorable for placer formation. Questions of the genesis of chromite placer occurrences in the Ural part of the East European Platform, their distribution and primary sources need further study.

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Bhat, Aadil, Anutosh Paria, A. Deepika, K. Sreedharan, M. Makesh, Megha K. Bedekar, C. S. Purushothaman et K. V. Rajendran. « Molecular cloning, characterisation and expression analysis of melanoma differentiation associated gene 5 (MDA5) of green chromide, Etroplus suratensis ». Gene 557, n^o 2 (février 2015) : 172–81. http://dx.doi.org/10.1016/j.gene.2014.12.028.

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Henry, Karen S., John C. Petura, Steven Brooks, Steven Dentico, Stephen A. Kessel et Mark Harris. « Preventing surface deposition of chromium with asphalt caps at chromite ore processing residue sites : a case study ». Canadian Geotechnical Journal 44, n^o 7 (1 juillet 2007) : 814–39. http://dx.doi.org/10.1139/t07-029.

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Caps were constructed on chromite ore processing residue (COPR) sites in the Kearny, New Jersey, area between 1989 and 1994 to prevent human exposure to hexavalent chromium (Cr(VI)). The caps comprise geotextile overlain by 100 mm of dense graded aggregate (DGA) and 100 mm of hot mix asphalt (HMA). Prior to constructing these "composite asphalt caps" (CACs), Cr(VI) was sometimes deposited on surface soils as chromate (salts) during evaporative periods. We initially thought the geotextile and DGA acted as a capillary barrier, stopping capillary water rise, but site inspection revealed that the DGA and geotextile were too moist to perform this function. Further study included a literature review, DGA capillary rise estimates, in situ measurement of soil-water content over 7 months at a representative COPR site, and numerical modeling of matric suction gradients induced by evaporation. The collective results reveal that the CACs eliminate upward matric suction gradients from the COPR–soil through the DGA, thereby precluding surface chromate deposition. Even during evaporative periods, the low unsaturated hydraulic conductivity of the HMA restricts upward movement of moisture and soluble chromate from underlying COPR–soil. In contrast, there are almost always upward matric suction gradients in uncapped COPR–soil.Key words: capillary rise, chromite ore processing residue, chromate, hexavalent chromium, composite asphalt cap, evaporation.

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Dey, Satarupa, Baishali Pandit et A. K. Paul. « Reduction of Hexavalent Chromium by Viable Cells of Chromium Resistant Bacteria Isolated from Chromite Mining Environment ». Journal of Mining 2014 (10 août 2014) : 1–8. http://dx.doi.org/10.1155/2014/941341.

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Environmental contamination of hexavalent chromium [Cr(VI)] is of serious concern for its toxicity as well as mutagenic and carcinogenic effects. Bacterial chromate reduction is a cost-effective technology for detoxification as well as removal of Cr(VI) from polluted environment. Chromium resistant and reducing bacteria, belonging to Arthrobacter, Pseudomonas, and Corynebacterium isolated from chromite mine overburden and seepage samples of Orissa, India, were found to tolerate 12–18 mM Cr(VI) during growth. Viable cells of these isolates were also capable of growing and reducing 100 μM Cr(VI) quite efficiently in Vogel Bonner (V.B.) broth under batch cultivation. Freshly grown cells of the most potent isolate, Arthrobacter SUK 1201, reduced 100 μM Cr(VI) in 48 h. Reduction potential of SUK 1201 cells decreased with increase in Cr(VI) concentration but increased with increase in cell density and attained its maximum at 1010 cells/mL. Chromate reducing efficiency of SUK 1201 was promoted in the presence of glucose and glycerol while the highest reduction was at pH 7.0 and 25°C. The reduction process was inhibited by divalent cations Ni, Co, and Cd, but not by Cu. Similarly, carbonyl cyanide m-chlorophenylhydrazone, N,N,-Di cyclohexyl carbodiimide, sodium azide, and sodium fluoride were inhibitory to chromate reduction, while 2,4 dinitrophenol promoted the process. Cells permeabilized by toluene increased the efficiency of Cr(VI) reduction and, thereby, indicate that Arthrobacter sp. SUK 1201, indigenous to chromite mining environment, could be used as an ideal tool for chromium bioremediation.

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Thèses sur le sujet "Chromide"

Niault, Théophile. « Étude du mécanisme de synchronisation de la réplication des deux chromosomes de Vibrio cholerae ». Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS121.

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Contrairement à la grande majorité des bactéries qui possèdent un chromosome unique, Vibrio cholerae, l'agent pathogène responsable de la maladie du choléra, contient un génome divisé en deux réplicons : un chromosome principal (Chr1) et un chromosome secondaire (Chr2). Les chromosomes secondaires sont apparus indépendamment dans de nombreux phylum bactériens et sont souvent associés à des caractères pathogènes ou symbiotiques (par exemple Leptospira, Agrobacterium, Burkholderia). Les chromosomes secondaires résultent de l'acquisition et de la domestication de grands plasmides. En effet, certains "mégaplasmides" ont cohabité avec leur hôte au cours d'une longue période évolutive et sont devenus un composant essentiel du génome de leur hôte. Au cours de leur domestication, les chromosomes secondaires ont acquis différentes caractéristiques permettant leur maintien à travers les divisions cellulaires assurant leur transfert vertical aux générations suivantes. L'étude des bactéries à génome multipartite permet de s'interroger sur le bénéfice sélectif d'un organisme à posséder plusieurs chromosomes. Ou encore, comment un élément génétique acquis horizontalement peut-il se connecter à un réseau génétique préétabli ? L'une des principales étapes de la domestication des mégaplasmides est leur intégration dans le cycle cellulaire de l'hôte. Chez V.cholerae, la réplication de Chr2 est coordonnée avec celle de Chr1. Chr1, qui est 3 fois plus grand que Chr2, est initié en premier et lorsque les 2/3 se sont répliqués, un signal d'initiation déclenche la réplication de Chr2 de sorte que les deux chromosomes terminent leur réplication de façon concomitante. Ce signal d'initiation est émis lorsque la fourche de réplication passe par un locus non codant de Chr1 nommé crtS (Chr2 Replication Triggering Site)2,3. Cependant, le mécanisme moléculaire à l'origine de ce signal d'initiation est encore très difficile à élucider. Notre travail vise à élucider le mécanisme de ce nouveau point de contrôle bactérien. Afin de s'attaquer à ce problème, nous avons développé plusieurs approches de pointe pour étudier le mécanisme à différents niveaux : -Echelle génomique : ChIPseq à haute résolution -Single-cell : microscopie à fluorescence -Moléculaire : CryoEM
Contrary to the vast majority of bacteria that possesses a unique chromosome, Vibrio cholerae, the pathogenic agent responsible for cholera disease, contains a genome divided into two replicons: a main chromosome (Chr1) and a secondary chromosome (Chr2). Secondary chromosomes appeared independently in many bacterial phylum and are often associated with pathogenic or symbiotic traits (i.e. Leptospira, Agrobacterium, Burkholderia). Secondary chromosomes result from the acquisition and domestication of large plasmids1. Indeed, some “megaplasmids” have cohabited with their host over a long evolutionary period and became an obligatory component of their host’s genome, essential for their normal metabolism. During their domestication, secondary chromosomes acquired different features allowing their maintenance through cell divisions ensuring their vertical transfer to subsequent generations. The study of multipartite genome bacteria allows questioning the selective benefit of an organism to possess several chromosomes. In addition, how can a horizontally acquired genetic element connect to a pre-established genetic network? One of the major steps in megaplasmid domestication is their integration into the host cell cycle. In V.cholerae, Chr2 replication is coordinated with that of Chr1. Chr1, which is 3 times larger than Chr2, is initiated first and when 2/3 has replicated, an initiation signal triggers the replication of Chr2 so that both chromosomes terminate replicating concomitantly. This initiation signal is emitted when the replication fork passes through a non-coding Chr1 locus named crtS (Chr2 Replication Triggering Site)2,3. However, the molecular mechanism behind this initiation signal is still very elusive. Our work aims to elucidate the mechanism of this novel bacterial replicative checkpoint. In order to tackle this problem we developed several cutting-edge approaches to study the mechanism at different levels: -Genomic scale: high resolution ChIPseq -Single cell: fluorescent microscopy -Molecular: CryoEM

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Del, Pianta Dimitri. « Détermination des paramètres physcio chimiques régissant l’électrodéposition d’une couche de chrome métallique à partir d’une solution de chrome trivalent ». Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3035/document.

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De par leurs propriétés mécaniques et anti-corrosion élevées, les revêtements métalliques de chrome sont utilisés dans de nombreux domaines tels que l’aéronautique, l’automobile, le ferroviaire, la défense,… Aujourd’hui le chromage dur industriel, réalisé à partir de chrome hexavalent, est fortement menacé par la directive européenne REACH qui prévoit l’interdiction d’utilisation de sels de chrome VI (classé CMR) à l’horizon 2017. Dans ce contexte le projet HCTC (Hard Chromium by Trivalent Chromium) regroupe 16 partenaires industriels et 2 partenaires académiques sous la coordination de l’Institut de Recherche Technologique Matériaux, Métallurgie, Procédés (IRT M2P) afin de développer une alternative à base de sel de chrome trivalent. Le développement d’un procédé de substitution à partir de sels de chrome trivalent nécessite de répondre aux interrogations liées notamment à la difficulté de réduire les ions Cr3+ formant en solution aqueuse un complexe hexa-aqua [Cr(H2O)6]3+ très stable et difficilement réductible. Afin de faciliter la réduction, l’ensemble des travaux recensés dans la littérature prône l’utilisation d’un agent complexant organique afin d’augmenter l’accessibilité du chrome. Une première partie de ce travail de thèse a été de caractériser les dépôts de chrome métallique réalisés à partir de la formulation de chrome III (EXDBA 1318) afin de mettre en évidence l’influence des paramètres de chromage (température du bain de traitement, densité de courant,…) sur les propriétés physico-chimiques des dépôts (Morphologie, cristallinité, composition chimique). Les résultats ont montré que la diminution de fissures tranversantes est généralement accompagnée d’une augmentation du taux de carbure de chrome qui dégrade l’état cristallin. La compréhension et l’optimisation du procédé a permis la réalisation de dépôts avec des propriétés physico-chimiques permettant de lancer les premiers essaies industriels dont les premiers retours sont très encourageants pour certaines applications (essentiellement automobile).Dans une deuxième partie plus fondamentale, des analyses par HPLC-ICP/AES ont mis en évidence la complexation du chrome par différents agents complexant. Les résultats obtenus ont montré que la complexation étaient d’autant plus importante que le pH est haut (pH=5) et le rapport molaire [Cr]/[Cplx] faible (1/10). Les mécanismes de réduction associés aux taux de complexation ont ensuite été déterminés par des mesures de voltammétrie cyclique en utilisant des électrodes sérigraphiées modifiées par de l’or. Les voltammogrammes obtenus montrent que la complexation du chrome par un agent complexant permet de passer d’un mécanisme de réduction en deux étape (Cr3+  Cr2+  Cr) en une seule (Cr3+  Cr).Une dernière partie du travail a été de définir l’influence de la chimie sur bain (pH et rapport molaire [Cr]/[Cplx]) sur les propriétés physico-chimiques des dépôts. Les résultats obtenus ont montré que pour des solutions faiblement complexées il est préférable de travailler à des pH bas et d’appliquer de faibles densités de courant (<15A/dm²) tandis qu’une augmentation du taux de complexation du chrome par l’agent complexant nécessite d’appliquer des densités de courant plus fortes. Ce travail a aussi permis de montrer l’existence d’une zone de pH optimale pour un rapport molaire [Cr]/[Cplx] donnée. L’existence de cette zone de pH révèle l’existence d’un domaine d’équilibre en solution, favorable à la réduction du chrome. L’ensemble de ces travaux plus fondamentaux ont permis d’améliorer les connaissances sur le procédé de chromage à partir d’un sel de chrome trivalent et ainsi de réfléchir à une nouvelle formulation pour des applications plus critiques où la solution actuelle a pu montrer quelques limites
Due to their high mechanical and anti-corrosion properties, chromium metal coatings are used in many fields such as aeronautics, automotive, railway, defense, etc. Today industrial hard chromium coating, made from of hexavalent chromium, is strongly threatened by the European REACH Directive, which provides for the prohibition of the use of chromium VI salts (classified as CMR) by 2017. In this context, the HCTC project (Hard Chromium by Trivalent Chromium) groups together 16 industrial partners and 2 academic partners under the coordination of the Institute for Materials, Metallurgy and Process Technology Research (IRT M2P) to develop an alternative based on trivalent chromium salt. The development of a substitution process from trivalent chromium salts requires answering the questions related in particular to the difficulty of reducing the Cr3+ ions forming in aqueous solution a very stable hexa-aqua [Cr(H2O)6]3+ complex and hardly reducible. In order to facilitate the reduction, all the works listed in the literature advocate the use of an organic complexing agent in order to increase the accessibility of chromium.A first part of this thesis work was to characterize the chromium metal deposits made from the chromium III formulation (EXDBA 1318) in order to highlight the influence of chromium parameters (bath temperature, density of current, ...) on physico-chemicals properties of the deposits (Morphology, crystallinity, chemical composition). The results showed that the decrease of transverse cracks is generally accompanied by an increase in chromium carbide which degrades the crystalline state. The understanding and the optimization of the process allowed the realization of deposits with physico-chemical properties allowing to launch the first industrial tests whose first returns are very encouraging for certain applications (mainly automobile).In a second, more fundamental part, HPLC-ICP / AES analyzes have demonstrated the complexation of chromium by different complexing agents. The results obtained showed that the complexation was all the more important that the pH is high (pH = 5) and the molar ratio [Cr] / [Cplx] low (1/10). Reduction mechanisms associated with complexation rates were then determined by cyclic voltammetry measurements using gold-modified screen-printed electrodes. The voltammograms obtained show that the complexation of chromium by a complexing agent makes it possible to go from a reduction mechanism in two steps (Cr3+  Cr2+  Cr) to a single one (Cr3+  Cr).A final part of the work was to define the influence of bath chemistry (pH and [Cr]/[Cplx] molar ratio) on the physico-chemical properties of coatings. The results obtained showed that for weakly complexed solutions it is preferable to work at low pH and to apply low current densities (<15A / dm²) while an increase in the chromium complexation rate by the complexing agent requires the application of higher current densities. This work also showed the existence of an optimal pH zone for a given [Cr]/[Cplx] molar ratio. The existence of this zone of pH reveals the existence of a balance domain in solution, favorable to the reduction of chromium. All of these more fundamental works have made it possible to improve the knowledge on the chromium plating process from a trivalent chromium salt and thus to think about a new formulation for more critical applications where the current solution has been able to show some limits

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Rolet, Jason. « Influence de la forme de l'onde de polarisation sur la microstructure et les propriétés de revêtements électrolytiques élaborés à base de chrome trivalent ». Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD010.

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Ce travail de thèse s’inscrit dans un projet de grande envergure piloté par l’IRT M2P, intitulé « Hard Chrome by Trivalent Chromium » qui regroupe 15 partenaires industriels et 2 partenaires académiques. L’objectif principal est de substituer les composés du chrome hexavalent par des électrolytes à base de chrome trivalent dans les procédés de chromage « dur », en réponse à l’application du règlement européen REACH en septembre 2017, même si des demandes d’autorisations temporaires sont en cours. Dans le cadre de cette thèse, des études électrochimiques ont été réalisées sur des bains commercial et synthétique. Celles-ci ont conduit au choix d’un matériau jouant le rôle d’anode, à une meilleure compréhension des mécanismes mis en jeu et de ce fait à une optimisation des conditions d’utilisation du bain commercial. D’autre part, une étude approfondie des courbes transitoires permet de mieux appréhender le comportement des électrolytes de chrome trivalent vis-à-vis des courants pulsés. Ainsi, un plan d’expérience sur les paramètres des pulses avec pour sortie de multiples caractérisations des dépôts de chrome montre que les courants pulsés influent sur plusieurs propriétés telles que : la teneur en carbone, la structure cristalline, la microdureté, la morphologie de surface et la microfissuration. Grâce au traitement des données issues du plan d’expériences, l’optimisation des paramètres de polarisation aboutit à l’élaboration de séquences de pulses optimisées. L’utilisation de celles-ci, employées seules ou en combinaison avec d’autres séquences de pulses issues également du plan d’expériences, aboutit à l’obtention de dépôts de chrome trivalent dont les propriétés sont modulables en fonction des paramètres procédés. Dans l’optique de la mise en place d’une nouvelle stratégie de choix des paramètres de l’impulsion anodique, un dispositif permettant la mesure du pH local en fonction des séquences et à proximité immédiate de la surface a été élaboré. Les premières tendances confirment les modes d’action des courants pulsés, et les choix qui ont été faits pour l’optimisation
This thesis work is part of an ambitious project handled by IRT M2P, named “Hard Chrome by Trivalent Chromium” which gathers 15 industrials partners but also 2 academic partners. The main objective is to substitute the hexavalent chromium compounds in hard chromium electroplating process before there ban by European instances (REACH, ECHA) in September 2017, excepted for those authorized. As part of this thesis, electrochemical studies were realized on commercial and synthetic baths. Thanks to this studies, a material has been chosen to act as an anode for the making of the trivalent chromium coatings ; furthermore, the utilization conditions of the commercial bath has been optimized. Moreover, another study based on transient curves allows a better comprehension of the behaviour of the trivalent chromium electrolytes regarding pulsed current. This work permitted the elaboration of pulse sequences in the form of an experimental design. The realization and characterization of trivalent chromium coatings as a part of the experimental design show that pulsed current have an effect on several properties of the coatings such as carbon content, crystalline structure, microhardness, surface morphologies an microcracking. Thanks to the analyses of the results from the experimental design, an optimization of pulsed current has been made to obtain optimized pulse sequences. The utilization of those pulse sequences, used alone or combine with some pulse sequences of the experimental design lead to the elaboration of trivalent chromium coatings which properties are adjustables depending on the set parameters of the process. To further optimize the properties of the coatings, the basis of an analysis tool based on local pH measurements are developed; this analysis tool must make it possible to select the most interesting pulse sequences for the realization of trivalent chromium coatings

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Yalcin, Sezgin. « Modeling Chromium Leaching From Chromite Ore Processing Waste ». Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1053412/index.pdf.

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Chromium has been widely used in many industrial applications. As a result of chromite ore processing, large amounts of chromite ore processing waste (COPW) material that can be classified as hazardous have been produced and released into the environment. Therefore, knowledge of migration behavior and leaching rates of chromium through waste materials and soils are of primary concern for environmentally sound management of land-disposal hazardous wastes. Haskö
k (1998) experimentally studied leaching rates of total Cr and Cr(VI) using laboratory columns packed with chromium COPW material produced by a sodium chromite plant. Based on the experimental results of Haskö
k (1998), present study aim, through mathematical modeling, to understand the dissolution kinetics of chromium during leaching of COPW material and to investigate the effectiveness of intermittent leaching involving a sequence of batch (dissolution) and leaching (mass flushing) operational modes. Obtained results show that a coupled system of two first order differential equations was able to capture the essential characteristics of leaching behavior of COPW material. In addition, the kinetics of chromium dissolution from COPW appeared to be controlled by the difference between aqueous phase concentration and a saturation concentration, by the mass fraction of dissolvable chromium remaining in the solid phase, and finally by the contribution of a constant dissolution rate manifested as a steady-state tailing behavior. As a result of performed simulations it was seen that intermittent leaching could be 65%and 35% more effective than continuous leaching for total Cr and Cr(VI), respectively.

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Eadie, Edward Norman. « Pattern of international trade in chromite and ferrochromium : an historical perspective / ». Title page, table of contents and abstract only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phe11.pdf.

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Oki, Makanjuola. « Conversion coatings on aluminium ». Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390302.

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Hu, Xianfeng. « Fundamental Studies on Direct Chromium Alloying by Chromite Ore with Designed Alloying Precursor ». Licentiate thesis, Luleå tekniska universitet, Mineralteknik och metallurgi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18117.

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Chromium is an important alloying element for stainless steels and other Cr-bearing steels. During the steelmaking process chromium is added to the steels mainly in the form of ferrochrome, which is largely produced by the energy-intensive smelting reduction process of chromite ore in the submerged arc furnace. To reduce the overall energy consumption during the ferrochrome production process and the chromium alloying process, direct chromiumalloying by chromite ore has been proposed. The application of this process will integrate the processes for ferrochrome production and chromium alloying, and thus has the potential to cut the production costs of the Cr-bearing steels by avoiding, or at least partially avoiding, the usage of ferrochrome. Further, this new alloying process has the capacity to improve therecovery of chromium from chromite ore. This thesis presents fundamental studies on the carbothermic reduction of synthetic iron chromite (FeCr2O4) and chromite ore, which aim at designing a direct alloying precursor to be applied in the industrial process. Thermogravimetric Analysis (TGA) experiments have been carried out to investigate the carbothermic reduction processes of FeCr2O4 in the absence/presence of metallic iron, and of chromite ore in the absence/presence of mill scale. In the case of using the mixture ‘FeCr2O4 +iron powder + graphite’, it is found that the presence of metallic iron enhances the reduction of FeCr2O4, and this enhancing effect increases with increasing iron addition. The enhancing effect of iron addition on the reduction of FeCr2O4 is due to the fact that the reduction of component Cr2O3 in FeCr2O4 is enhanced, and this effect is attributed to the presence of solidiron which can decrease the activity of chromium by having chromium in situ dissolved in the iron. In the case of using the mixture ‘chromite ore + petcoke’, it is found that the reduction of iron ions in the chromite ore starts before that of chromium ions in the ore and the reduction of iron ions and chromium ions in the ore overlaps to some degree. (Cr,Fe)7C3 is found to bethe intermediate phase during the reduction and a chromium gradient is found in the spinel phase of the fractional reduced sample at 1673 K. A four-stage reduction process is proposed: one stage involving the reduction of iron ions in the chromite ore and three stages involving the reduction of chromium ions in the ore. The activity aspects of component FeCr2O4 and component MgCr2O4 in the chromite ore have been considered. The difficulty in the reductionof the chromite ore is attributed to the fact that, as the reduction proceeds, the activity of component MgCr2O4 in the fractional reduced ore will decrease to a very low level, which makes the further reduction very difficult. In the case of using the mixture ‘chromite ore + mill scale + petcoke’, it is found that mill scale is reduced to iron before 1573 K. The asreduced iron is disseminated around chromite ore particles and, at the same time, some carbonis dissolved in the iron via diffusion. Reduction of chromite ore is enhanced with the addition of mill scale at temperatures higher than 1623 K, and the enhancing effect increases with increasing mill scale addition. The enhancing effect, in this case, is attributed to the presence of molten Fe-Cr-C phase in the vicinity of chromite ore, which can decrease the activity of chromium by having chromium in situ dissolved into the melt. Induction furnace experiments have been carried out to investigate the effectiveness of some different alloying mixtures. The experimental results have confirmed the necessity ofadjusting the composition of the slag to ensure high chromium yield in the final product and the experimental results show that, by using iron scrap, chromium yield can reach 90%. The present findings have led to the proposal of using ‘chromite ore + mill scale + petcoke’ as alloying precursor for direct chromium alloying. The effectiveness of this alloying precursor needs to be further explored by induction furnace experiments, followed by full scale Electric Arc Furnace experiments.

Godkänd; 2014; 20141027 (andbra); Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Xianfeng Hu Ämne: Processmetallurgi /Process Metallurgy Uppsats: Fundamental Studies on Direct Chromium Alloying by Chromite Ore with Designed Alloying Precursor Examinator: Professor Bo Björkman Institutionen för samhällsbyggnad och naturresurser Avdelning Mineralteknik och metallurgi Luleå tekniska universitet Diskutant: Professor Timo Fabritsius University of Oulu Finland Tid: Fredag den 15 december 2014 kl 10.00 Plats: E246, Luleå tekniska universitet

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Makatera, F. S. « Galvanic coating with chrome : features, technologies and methods of coating the surface of metals with chromium ». Thesis, Київський національний університет технологій та дизайну, 2018. https://er.knutd.edu.ua/handle/123456789/11380.

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Plecháč, David. « OS Google Chrome - teorie a praxe ». Master's thesis, Česká zemědělská univerzita v Praze, 2017. http://www.nusl.cz/ntk/nusl-315941.

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The thesis is focused on the characteristics of the key features of the operating system Google Chrome OS and on the evaluation of deployment of this operating system in practise. The theoretical part describes the purpose and philosophy of the commercial operating system Google Chrome OS and its relation with Chrome web browser. The connection with open-source projects Chromium and Chromium OS is explained. Details of application development and deployment options, in the form of virtualization and domain administration, are analysed. The practical part applies theoretical knowledge from the development of applications for Chrome OS to create thin client application for remote control of hardware sensor over the internet. This sensor is designed and built on the platform Arduino. The sensor measures the temperature and humidity of the ambient air and remote controls high-voltage switching relays. Communication over TCP/IP uses modern MQTT protocol, for which the server is configured with MQTT Broker Mosquitto. The next section demonstrates the procedure for building a customized build of Chromium OS from the publicly provided Google source codes. Based on the evaluation of the acquired theoretical and practical knowledge, I assess the possibility of deploying the Chrome OS in private and commercial areas.

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Ustaoglu, Emre. « Optimization Of Conditions In Sulfuric Acid Leaching Of Turkish Chromite Concentrates ». Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607344/index.pdf.

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In this thesis work, a high grade chromite concentrate obtained from PinarbaSi, Kayseri region of Turkey was reacted with sulfuric acid solution to determine the optimum conditions of leaching of chromite ores. Conventional methods for producing chromium are still valid in industry. The main process in production includes soda melting and taking it into solution in the form of chemical compounds such as sodium dichromate. Three and six valence states of chromium have importance in production. Trivalent chromium, chrome ore or chromite have no harmful effects. However, compounds of hexavalent chromium show toxic, irritating and corrosive action to people and environment. In the mentioned conventional method, main products consist of hexavalent chromium compounds. In this study, only trivalent chromium remained in the leach solution and did not change to hexavalent state. Obtained product after leaching was chromium(III) sulfate. The maximum extraction of chromium in the absence of perchloric acid was 94.1 % under the conditions of 175 °
C, 6 hours and 84.6 wt % sulfuric acid. The maximum extraction of chromium in the presence of perchloric acid was 98.7 % under the conditions of 175 °
C, 2 hours, 84.6 wt % sulfuric acid and ½
perchloric acid / chromite ratio. The latter one was also the highest recovery value obtained during the experiments. Moreover, in none of the analyzed samples, appreciable amounts of hexavalent chromium was found during analyses.

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Livres sur le sujet "Chromide"

B, Daellenbach C., dir. Chromium-chromite : Bureau of Mines assessment and research : proceedings of Bureau of Mines briefing held at Oregon State University, Corvallis, OR, June 4-5, 1985. [Avondale, Md.] : U.S. Dept. of the Interior, Bureau of Mines, 1986.

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Hundley, Gary L. Extraction of chromium from domestic chromites by alkali fusion. Pgh. [i.e. Pittsburgh] PA : U.S. Dept. of the Interior, Bureau of Mines, 1985.

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Visnapuu, A. Upgrading domestic high-iron chromite concentrates by carbonyl extraction of excess iron. Pittsburgh, Pa : U.S. Dept. of the Interior, Bureau of Mines, 1985.

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Midwest Research Institute (Kansas City, Mo.) et United States. Environmental Protection Agency. Office of Air Quality Planning and Standards., dir. Chromium emissions from chromium electroplating and chromic acid anodizing operations : Background information for proposed standards. Research Triangle Park, NC : U.S. Environmental Protection Agency, Office of Air and Radiation, Office of Air Quality Planning and Standards, 1993.

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United States. Environmental Protection Agency. Office of Air Quality Planning and Standards, dir. Chromium emissions from chromium electroplating and chromic acid anodizing operations : Background information for promulgated standards. Research Triangle Park, N.C : U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, 1994.

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Mines, India Ministry of. Monograph on chromite. [New Delhi] : Government of India, Ministry of Mines, 2013.

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Michalik, Marek. Effect of water vapour on growth and adherence of chromia scales on pure chromium. Jülich : Forschungszentrum Jülich, 2007.

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Papp, John F. Chromium. [Washington, D.C.?] : Bureau of Mines, U.S. Dept. of the Interior, 1985.

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United States. Agency for Toxic Substances and Disease Registry. Division of Toxicology and Environmental Medicine. Chromium. Atlanta, GA : Dept. of Health and Human Services, Agency for Toxic Substances and Disease Registry, Division of Toxicology and Environmental Medicine, 2008.

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Papp, John F. Chromium. Washington, D.C : U.S. Department of the Interior, Bureau of Mines, 1991.

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Chapitres de livres sur le sujet "Chromide"

Durand, B., J. M. Paris, E. C. Behrman, A. Huang et A. Wold. « Divalent Metal Chromium(III) Oxides (Chromites) ». Dans Inorganic Syntheses, 50–53. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470132517.ch15.

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Sarkar, Ritwik. « Chromite and MgO–Cr2O3 Refractories (Chrome–Mag and Mag–Chrome) ». Dans Refractory Technology, 169–79. 2^e éd. Boca Raton : CRC Press, 2023. http://dx.doi.org/10.1201/9781003227854-10.

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Kunnmann, W., et D. Bellavance. « Magnesium Chromite ». Dans Inorganic Syntheses, 134–39. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470132456.ch26.

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Misra, Kula C. « Chromite Deposits ». Dans Understanding Mineral Deposits, 238–72. Dordrecht : Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-3925-0_5.

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Castroviejo, Ricardo. « Chromite (chr) ». Dans A Practical Guide to Ore Microscopy—Volume 1, 183–89. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-12654-3_30.

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Bhowmick, Sanjit, Gavin Le, Atul Verma et Prabhakar Singh. « Assessment of Chromium Evaporation from Chromia and Alumina Forming Alloys ». Dans Ceramic Engineering and Science Proceedings, 115–24. Hoboken, NJ, USA : John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118095249.ch10.

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Kurtz, Wolfgang, et Hans Vanecek. « Chromium ». Dans W Tungsten, 115–21. Berlin, Heidelberg : Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-662-08690-2_19.

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Vasiliu, Monica, et David A. Dixon. « Chromium ». Dans Encyclopedia of Earth Sciences Series, 1–2. Cham : Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-39193-9_59-1.

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Vasiliu, Monica, et David A. Dixon. « Chromium ». Dans Encyclopedia of Earth Sciences Series, 255–56. Cham : Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-39312-4_59.

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Crowson, Phillip. « Chromium ». Dans Minerals Handbook 1992–93, 62–68. London : Palgrave Macmillan UK, 1992. http://dx.doi.org/10.1007/978-1-349-12564-7_10.

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Actes de conférences sur le sujet "Chromide"

Nagaraj, B. A., D. J. Wortman, A. F. Maricocchi, J. S. Patton et R. L. Clarke. « Development of Corrosion Resistant Coatings for Marine Gas Turbine Applications ». Dans ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-200.

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The performance of a number of selected diffusion and overlay coatings was evaluated using an atmospheric pressure burner rig; the test environment contained compounds of vanadium, sodium and sulfur. The tests were designed to simulate the deposit chemistry and sulfur trioxide partial pressures expected in a marine gas turbine engine operating on contaminated fuel. The tests were performed for up to 1000 hours at 1300°F and 1650°F. At 1650°F, virtually all the coatings tested were severely corroded, emphasizing the necessity of improved coating materials such as ceramics to resist vanadic corrosion. At 1300°F, FeCrAlY, pack chromide and CoCrAlY coatings with high chromium performed well. Yttria stabilized zirconia coatings, with selected bond coats, were evaluated with fuels containing low (0.3ppm) and high (21ppm) concentrations of vanadium in atmospheric burner rig at 1650°F. Reaction products, primarily yttrium vanadate, were observed in both tests. The results are discussed in terms of bond coat corrosion and chemistry of the test environment.

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Kislov, E. V., V. S. Kamenetsky et E. A. Belousova. « CHROMITITES OF THE MAIN SARANOVSKOYE FIELD, PERM TERRITORY : COMPOSITION AND GENESIS ». Dans Проблемы минералогии, петрографии и металлогении. Научные чтения памяти П. Н. Чирвинского. Пермский государственный национальный исследовательский университет, 2021. http://dx.doi.org/10.17072/chirvinsky.2021.95.

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The chromitites mineral composition from the Central ore body of the Main Saranovskoye deposit has been studied. Development of chromite grains in silicate interstices; constancy of its composition, idiomorphism; increased chromium content of small and periphery of large chromite grains; absence of corrosion, substitution with chrome magnetite or chlorite; xenomorphic high chromium chromite; association with chromium-containing minerals and minerals of hydrothermal origin; joint growth of chromite with uvarovite; predominance of minerals with Na and H2O in inclusions in chromite; inclusions of idiomorphic grains and chlorite laths, massicot crystals; the inclusion of laurite with a crystallographically faceted inclusion of chalcocite, chromite in the diabase skarn indicates that chromite was not a source of chromium for other minerals, but was formed together with hydrothermal minerals in the course of a single process. This is also evidenced by the composition of apatite: a high Y content and a negative Eu anomaly.

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Podob, Mark. « Chemical Vapor Deposition (CVD) Coatings for Protection of Jet Engine Components ». Dans ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/93-gt-375.

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CVD coatings are thin films resulting from the chemical reaction between a gaseous phase and the heated surface of a substrate. Among the industries using CVD coating technology are electronics, tooling, fuel cogeneration, and aerospace. The electronics industry uses CVD to deposit semiconductor materials onto different substrates. For the tooling industry, titanium nitride (TiN), titanium carbide (TiC), or aluminum oxide (Al2O3) is deposited onto cutting or metal forming tools. These hardcoatings act as chemical and thermal barriers between the tool and workpiece. In the aerospace industry, CVD is used to deposit aluminide or chromide coatings onto jet engine blades and other hot section components. The coatings improve the corrosion and oxidation resistance of the base metal. CVD is replacing older established methods for protecting these same components. While the use of CVD coatings in the aerospace industry is relatively new, it is gaining increasing acceptance. In addition to producing aluminides and chromides, CVD reactions can form coatings containing silicon, yttrium, hafnium and other rare earth elements. Since the coatings are the result of the chemical reaction between high purity gases and solids, coatings can be free of porosity and inclusions.

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Lalomov, A. V., I. R. Rakhimov, A. V. Grigorieva et Sh R. Zailyamov. « CHROMITE CONTENT OF THE PERMIAN-JURASSIC DEPOSITS OF THE VOLGA-URAL BASIN ». Dans Проблемы минералогии, петрографии и металлогении. Научные чтения памяти П. Н. Чирвинского. Пермский государственный национальный исследовательский университет, 2021. http://dx.doi.org/10.17072/chirvinsky.2021.113.

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The chromite content of the Permian and Jurassic deposits of the East European platform’s Eastern part, adjacent to the Urals - the Lukoyanovskoye field and the Sabantuy occurrence, has been established. The economic significance of the Lukoyanovskoe placer chromites is justified by the technology of extracting chromite concentrate, and the Sabantuy paleoplacer has good prospects because of high chromium content in the ore (Cr2O3 15–17 wt%).

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Kamolpornwijit, Wiwat, et Jay N. Meegoda. « Chrome Steel from Chromium Ore Processing Residue ». Dans Geo-Frontiers Congress 2011. Reston, VA : American Society of Civil Engineers, 2011. http://dx.doi.org/10.1061/41165(397)133.

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Järvinen, V., et T. Halkoaho. « Formation of poikilitic chromite in the basal dunite series of the 2.44 Ga Näränkävaara layered intrusion ». Dans Project KO5125 ARLIN Arctic Layered Intrusions as a Source of Critical Metals for Green Economy European Neighbourhood Instrument Cross-Border Cooperation Programme Kolarctic 2014-2020. GI KSC RAS, 2022. http://dx.doi.org/10.31241/arlin.2022.004.

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Poikilitic chromite has been described only from komatiitic cumulates with >Fo91–92. Its formation is thought to be related to high temperatures inhibiting chromite nucleation. Here, we describe poikilitic chromites found in the olivine adcumulate (Fo<91) basal dunite series of the Näränkävaara intrusion, and suggest a formation mechanism for poikilitic chromite in intrusive settings whereby low oxygen fugacity in the parental magma inhibits chromite nucleation. Results of this and other recent studies from the Näränkävaara intrusion are summarized, and implications for massive sulfide exploration in Fennoscandian 2.44 Ga intrusions are presented.

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Bondarenko, I. V., et E. I. Kuldeyev. « Beneficiation of fine chromite slurry at Donskoy Mining and Beneficiation Plant JSC on concentration tables to produce hard chromite pellets ». Dans Challenges of Science. Institute of Metallurgy and Ore Beneficiation, Satbayev University, 2021. http://dx.doi.org/10.31643/2021.13.

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Processing industrial products and technogenic waste is an important task in the mining and metallurgical industry. In Kazakhstan, the processing of chrome ore from the Kempirsay group of deposits has produced more than 15 million tonnes of slurry tailings containing up to 30 wt% chrome oxide. The best results in the world for the processing of fine chromium raw materials are shown by Turkish enterprises with the use of the separation of slurries by size classes and beneficiation on concentration tables. The authors conducted researches for beneficiation of chrome slurry from Dubersay tailings pond (Kazakhstan) with the use of similar technological methods that enabled to obtain concentrates with chrome oxide content of 51 wt% and increasing the yield of beneficiated fine-graded chrome concentrates by 14% as compared with the existing beneficiation process. Strong chromium pellets with a crushing resistance of over 5000 N/pellet were produced from the rich chromium concentrates with the use of the ferrofluxing iron-calcium-silica binder technology by roasting the composition consisting of rich chromium concentrate, ferrous diatomite, and intermediate products and wastes of the chromium industry.

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Poll, R., et N. Miller. « 212. Determination of Hexavalent Chromium Exposure in Mixed Chromate Environments ». Dans AIHce 1997 - Taking Responsibility...Building Tomorrow's Profession Papers. AIHA, 1999. http://dx.doi.org/10.3320/1.2765339.

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Laul, Komal, Suebali Rahemanji, Ravi Shankar, Richard Fenton, Carl Perrin et Andrew McMillan. « Improved Blade Tips for Abradable Coatings used in Gas Turbines ». Dans ITSC 2012, sous la direction de R. S. Lima, A. Agarwal, M. M. Hyland, Y. C. Lau, C. J. Li, A. McDonald et F. L. Toma. ASM International, 2012. http://dx.doi.org/10.31399/asm.cp.itsc2012p0166.

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Abstract Gas turbine efficiency is of paramount importance in the modern carbon conscious global economy and the industry is always looking for ways to improve the efficiency of gas turbine engines. Gas bypass between the rotating turbine blade tip and the engine casing affects both the efficiency and the power output of an engine. An increase in this clearance of 125µm can result in an increase of 0.5% in specific fuel consumption. Abradable coatings have been designed to allow the turbine blade abrasive tip to cut a path into shroud abradable coating to improve the seal between the blade tip and the casing. A holistic approach to improving the abradable system – the abradable coating and the blade tip – is necessary. Better blade tips can result in use of denser, more erosion resistant abradables improving performance of the whole system. Current blade tips are limited as the matrix oxidizes at high temperature losing its ability to hold as well as protect the CBN particles. Improvement in blade tips – both in the cutting particles and the matrix which hold these particles – will therefore improve the abradable system performance, as well as allow the use of denser, more erosion resistant abradable materials. This paper represents efforts to improve the matrix oxidation resistance which holds CBN particles. The matrix is a low-aluminum MCrAlHf which is further aluminized to improve the oxidation resistance. New coatings being tested are enhanced aluminide coatings, platinum aluminide coatings and platinum chromide aluminide coatings. The results will be discussed in terms of matrix composition and microstructure as deposited and after static oxidation. The effect of matrix and its impact on the blade tip performance will also be reviewed.

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Meegoda, Jay N., Wiwat Kamolpornwijit, Zhengbo Hu, Robert Mueller et Ravi Patraju. « Conversion of Chromium Ore Processing Residue to Chrome Steel ». Dans GeoCongress 2008. Reston, VA : American Society of Civil Engineers, 2008. http://dx.doi.org/10.1061/40970(309)48.

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Rapports d'organisations sur le sujet "Chromide"

Brenan, J. M., K. Woods, J. E. Mungall et R. Weston. Origin of chromitites in the Esker Intrusive Complex, Ring of Fire Intrusive Suite, as revealed by chromite trace element chemistry and simple crystallization models. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328981.

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To better constrain the origin of the chromitites associated with the Esker Intrusive Complex (EIC) of the Ring of Fire Intrusive Suite (RoFIS), a total of 50 chromite-bearing samples from the Black Thor, Big Daddy, Blackbird, and Black Label chromite deposits have been analysed for major and trace elements. The samples represent three textural groups, as defined by the relative abundance of cumulate silicate phases and chromite. To provide deposit-specific partition coefficients for modeling, we also report on the results of laboratory experiments to measure olivine- and chromite-melt partitioning of V and Ga, which are two elements readily detectable in the chromites analysed. Comparison of the Cr/Cr+Al and Fe/Fe+Mg of the EIC chromites and compositions from previous experimental studies indicates overlap in Cr/Cr+Al between the natural samples and experiments done at &gt;1400oC, but significant offset of the natural samples to higher Fe/Fe+Mg. This is interpreted to be the result of subsolidus Fe-Mg exchange between chromite and the silicate matrix. However, little change in Cr/Cr+Al from magmatic values, owing to the lack of an exchangeable reservoir for these elements. A comparison of the composition of the EIC chromites and a subset of samples from other tectonic settings reveals a strong similarity to chromites from the similarly-aged Munro Township komatiites. Partition coefficients for V and Ga are consistent with past results in that both elements are compatible in chromite (DV = 2-4; DGa ~ 3), and incompatible in olivine (DV = 0.01-0.14; DGa ~ 0.02), with values for V increasing with decreasing fO2. Simple fractional crystallization models that use these partition coefficients are developed that monitor the change in element behaviour based on the relative proportions of olivine to chromite in the crystallizing assemblage; from 'normal' cotectic proportions involving predominantly olivine, to chromite-only crystallization. Comparison of models to the natural chromite V-Ga array suggests that the overall positive correlation between these two elements is consistent with chromite formed from a Munro Township-like komatiitic magma crystallizing olivine and chromite in 'normal' cotectic proportions, with no evidence of the strong depletion in these elements expected for chromite-only crystallization. The V-Ga array can be explained if the initial magma responsible for chromite formation is slightly reduced with respect to the FMQ oxygen buffer (~FMQ- 0.5), and has assimilated up to ~20% of wall-rock banded iron formation or granodiorite. Despite the evidence for contamination, results indicate that the EIC chromitites crystallized from 'normal' cotectic proportions of olivine to chromite, and therefore no specific causative link is made between contamination and chromitite formation. Instead, the development of near- monomineralic chromite layers likely involves the preferential removal of olivine relative to chromite by physical segregation during magma flow. As suggested for some other chromitite-forming systems, the specific fluid dynamic regime during magma emplacement may therefore be responsible for crystal sorting and chromite accumulation.

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Kuster, K., C. M. Lesher et M. G. Houlé. Geology and geochemistry of mafic and ultramafic bodies in the Shebandowan mine area, Wawa-Abitibi terrane : implications for Ni-Cu-(PGE) and Cr-(PGE) mineralization, Ontario and Quebec. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329394.

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The Shebandowan Ni-Cu-(PGE) deposit occurs in the Shebandowan greenstone belt in the Wawa-Abitibi terrane. This deposit is one of a few economic Ni-Cu-(PGE) deposits in the Superior Province and one of a very few deposits worldwide that contains both Ni-Cu-(PGE) and Cr-(PGE) mineralization. The mafic-ultramafic successions in the area comprise abundant flows and sills of tholeiitic basalt and lesser Al-undepleted komatiite (MgO &gt;18 wt%, Al2O3/TiO2 = 15-25), the latter indicating separation from mantle sources at shallow levels. Siliceous high-Mg basalts (MgO 8-12 wt%, SiO2 &gt; 53 wt%, TiO2 &lt; 1.2 wt%, La/Sm[MN] &lt; 1-2) are relatively abundant in the area and likely represent crustally contaminated komatiites. Ultramafic bodies in the Shebandowan mine area comprise at least three or four komatiitic sills (A-B, C, D) and at least two komatiitic flows (E, F), all of which are altered to serpentinites or talc-carbonate schists with relict igneous chromite and rare relict igneous orthopyroxene-clinopyroxene. Unit A-B contains pentlandite-pyrrhotite-chalcopyrite-pyrite-magnetite mineralization, occurring as massive sulfides, sulfide breccias, or stringers, and subeconomic chromite mineralization in contorted massive bands varying from a few millimetres up to 10 metres thick. The localization of massive and semi-massive Ni-Cu-(PGE) ores along the margins of Unit A and the paucity of disseminated and net-textured ores suggest tectonic mobilization. Chromite is typically zoned with Cr-Mg-Al-rich (chromite) cores and Fe-rich (ferrichromite/magnetite) rims due to alteration and/or metamorphism, but rarely contains amoeboid magnetite cores. The thickness of chromite in Unit B is too great to have crystallized in cotectic proportion from the komatiitic magma and a model involving dynamic upgrading of magnetite xenoliths derived from interflow oxide facies iron formations is being tested.

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Andrews, P. R. A. Chromite. Natural Resources Canada/CMSS/Information Management, 1992. http://dx.doi.org/10.4095/328637.

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Sopok, Samuel. Determination of Chromic Acid in Chromium Plating Solutions Using a Redox Titration and Indicator. Fort Belvoir, VA : Defense Technical Information Center, août 1989. http://dx.doi.org/10.21236/ada220641.

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Duke, J. M. Stratiform chromite. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/208048.

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Duke, J. M. Podiform (ophiolitic) chromite. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/208050.

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Duke, J. M. Mafic/ultramafic-hosted chromite. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/208046.

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Duke, J. M. Gîtes stratiformes de chromite. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/208049.

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Klueh, R. L., D. J. Alexander et P. J. Maziasz. Low-chromium reduced-activation chromium-tungsten steels. Office of Scientific and Technical Information (OSTI), octobre 1996. http://dx.doi.org/10.2172/414871.

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Duke, J. M. Gîtes podiformes (ophiolitiques) de chromite. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1995. http://dx.doi.org/10.4095/208051.

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