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Academic literature on the topic 'Serpentine'
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Dissertations / Theses on the topic "Serpentine"
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Mann, Jason Peter. "Serpentine Activation for CO2 Sequestration." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12054.
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Serpentinite calcination currently represents a key step for its activation within ex situ aqueous mineral carbonation. However, the dehydroxylation kinetics that govern this process remain largely unresolved within literature. Available Arrhenius parameters (i.e. A and E) span a wide range of values and appear correlated in terms of a kinetic compensation effect (i.e. linear relationship between loge(A) and E). Following this observation, a revised model for dehydroxylation is presented, validated against a systematic investigation into the role of particle size on the dehydroxylation rate for both South West Oregon and New England Australia Serpentinite using non-isothermal TGA. Within these experiments, dehydroxylation occurs primarily through a particle size dependent mechanism, best described by the canonical spherical, retreating interface model (R3), with statistically equivalent Arrhenius parameters reported between specimens. Examining the processing side of activation, this thesis additionally explores the role of flash calcination, where dehydroxylation is achieved in extremely short residence times (<2 s) through the use of high temperatures (>1073 K) and rapid heating rates (>104 K/s). High temperatures required by this technique however, led to instant deactivation of the calcine through recrystallisation of the dehydroxylated phase to the high temperature product, forsterite. Investigation into this phase transition indicates magnesium leachability declines proportionally to the extent of forsterite content. Kinetic parameters for this transition are reported, allowing quantification of this deactivation process as a function of calcination temperature, time, and particle size. Closing this thesis, the dissolution of activated serpentinite within the CO2-H2O system is examined at conditions relevant to ex situ mineral carbonation (10 MPa, 423 K), with emphasis on reaction pressure, temperature, and particle size on the magnesium leaching rate.
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Merkulova, Margarita. "Comportement du fer et d'autres ions échangeurs d'électrons en contexte de subduction." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAU030/document.
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Les zones de subduction sont les plus grands systèmes de recyclage de notre planète. Elles permettent le recyclage de l'eau contenue dans la croûte océanique hydratée et de la lithosphère du manteau supérieur. L'eau joue un rôle clé dans de nombreux processus associés aux zones de subduction, comme la tectonique des plaques, la production de magma, le transport élémentaire et la génération de tremblement de terre. La composition chimique, le contenu H2O de la lithosphère océanique, l'âge et la géométrie de la plaque océanique sont les principaux facteurs contrôlant les processus de subduction, y compris la déshydratation.L'objectif principal de cette thèse est d'étudier le régime de la libération de l'eau depuis la plaque océanique subductante et le comportement du Fe et du S en contenus dans les serpentinites, qui représentent la principale lithologie de roche hydratées océaniques. L'approche expérimentale de ce travail permet d’étudier les changements chimiques et minéralogiques associés lors la déshydratation des serpentinites de différentes compositions. Un certain nombre de techniques d'analyse ont été utilisées pour étudier l’influence de la composition de la roche totale sur la composition des assemblages produits. Les intervalles de pression de température expérimentalement étudiés, à savoir 2 GPa et 450-900C, représentent des zones de subduction chaudes. L'extrapolation à d'autres gradients géothermiques communs a été faite par thermodynamique. Les compositions de serpentinite étudiées correspondent aux péridotites serpentinisées naturelles décrites pour la lithosphère océanique.Mon travail indique que la teneur en Fer contrôle a stabilité thermique d’antigorite. Déshydratation de serpentinites avec Fe, par conséquent, pasee à des températures plus basses par rapport aux assemblages Fe-libres. La déshydratation observée dans les systèmes sans Fer se fait le long d'une réaction univariante, alors que dans les systèmes contenant du Fer, la déshydratation se fait sur un domaine de température (réactions de déshydratation divariantes). De plus, la présence de Al dans serpentinite stabilise clinochlore, qui conserve 15% de l'eau initiale jusqu'à ~ 120 km (820°C/2 GPa) dans subduction chaud. Cette dépendance sur Fe et Al apporte importance de considérer non seulement la géométrie et l'âge de la plaque océanique, mais aussi une composition de lithologies lors de la modélisation et d’interprétation de subduction. Une comparaison entre la profondeur des séismes et la profondeur de déshydratation des serpentinites indique une possible contribution de la libération de l'eau à la sismicité dans les zones de subduction chaudes et à pente faible.La spectroscopie d'absorption des rayons X montre une réduction progressive de Fe et de S dans des serpentinites. Le rapport Fe3+/ Fetotal, de la roche totale, élevé dans la serpentinite, diminue dans les assemblages anhydres de haute température par décomposition de la magnétite (< 550°C) et de l’antigorite (700°C). La pyrite des serpentinites se transforme en pyrrhotite en-dessous de 450°C et induit une libération de ¼ de soufre initial, probablement sous forme de H2S. La magnétite et la pyrite présentes dans des serpentinites, sont des phases cruciales pour la production de fluides très oxydés et d’espèces volatiles soufrées qui peuvent être transportés depuis la plaque subductée vers le coin mantellique. Application des résultats montre que les fluides s’élevant de la plaque océanique sont responsables de l'oxydation du manteau; et décomposition de la magnétite et l’antigorite avec au moins 100°C différence peut provoquer une libération de fluides chimiquement différents à peu profond (basse-T) et profondes (T-élevé) parties de subduction<br>Subduction zones are the largest recycling systems of our planet. Subduction zones involve recycling of water from hydrated oceanic crust and lithosphere to the upper mantle. Water plays a key role in subduction zone processes, including plate tectonics, magma generation, elemental transport and earthquake generation. The chemical composition, H2O content of oceanic lithosphere sinking to the mantle, age and geometry of subducting oceanic slab are the main factors controlling subduction zone processes including dehydration.The principle aim of this dissertation is to investigate the regime of water release from subducting oceanic plate and the associated behavior of Fe and S in serpentinites, which are the main carriers of water into the slab. The experimental approach of my work allows one to compare chemical and mineral changes occurred during dehydration of serpentinites with different composition. A number of analytical techniques were applied to study the influence of bulk rock composition on the mineral chemistry of produced assemblages. The experimentally investigated pressure-temperature ranges, i.e. 2 GPa and 450-900C, are representative for hot subduction zones. The extrapolation to other common geothermal gradients was done through thermodynamic modeling. The investigated serpentinite compositions correspond to natural serpentinized peridotites described for oceanic lithosphere.Bulk Fe content was demonstrated to decrease thermal stability of antigorite by 25C on average. Dehydration of Fe-bearing serpentinites, consequently, occurs at lower temperatures compared to Fe-free assemblages. Dehydration reactions observed in Fe-free systems are univariant reactions, while in Fe-bearing systems, serpentinites dehydration appears over a range of temperature through divariant reactions. Moreover, the presence of Al in serpentinite stabilized clinochlore, which retains 15% water initial contain in serpentinite down to ~120km (820°C/2 GPa) within hot subduction. Such a dependence of serpentinite dehydration on bulk Fe and Al brings importance of considering not only geometry and the age of the slab, but also a composition of slab lithologies while modeling and interpreting processes in subduction zone. A comparison of the depths of serpentinite dehydration and seismicity revealed a strong correlation and therefore a potential contribution of water release to seismicity in the case of hot subduction zones (i.e., Chili type subduction).X-ray absorption spectroscopy measurements revealed a progressive reduction of Fe and S in investigated serpentinites. The bulk Fe3+/Fetotal ratio initially high in serpentinite is shown to decrease in anhydrous and higher temperature assemblages due to magnetite and Fe3+-bearing antigorite breakdown at <550°C and 700°C, respectively. The presence of pyrite in serpentinite, which transforms to pyrrhotite below 450°C, imposes a release of ¼ of initial sulfur, in H2S form. The presence of magnetite and pyrite in serpentinite, is crucial and responsible for the production of highly oxidized fluids and volatile sulfur species, which can be transported from the subducting slab into the mantle wedge. Application of results, obtained in the present study, to nature demonstrates that fluids rising from subducting slab are responsible for oxidation of overlying mantle, and in addition, magnetite and antigorite breakdown which occurs with at least 100°C difference may cause a release of chemically different fluids at shallow (low-T) and deep (high-T) parts of subduction
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McIntyre, Todd Ian. "Analysis of selected ions in Allium cratericola growing on serpentine and non-serpentine soil." Scholarly Commons, 1991. https://scholarlycommons.pacific.edu/uop_etds/2212.
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The primary problems which plants growing on serpentine soil must overcome are high magnesium concentrations and calcium deficiency. The ability of Allium cratericola to successfully exploit both serpentine and non-serpentine habitats may be due to physiological adaptations which compensate for unusual mineral composition of the soil. Although the Table Mountain soil is described as non serpentine, it bears ionic similarities to the three serpentine soils studied in this investigation.
With the advent of modern biochemical techniques in plant physiology, there are ample opportunities to expand on past work concerning plant growth on serpentine soil. Investigations into the biochemical nature of tolerance mechanisms, especially those involving the mechanics of ion transport and translocation, could further elucidate the nature of plant growth on this soil type.
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Can, Semra. "Characterization Of Serpentine Filled Polypropylene." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609434/index.pdf.
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ABSTRACT
CHARACTERIZATION OF SERPENTINE FILLED POLYPROPYLENE
Can, Semra
Ph.D., Department of Polymer Science and Technology
Supervisor: Prof. Dr. Teoman Tinç<br>er
March 2008, 158 pages
In this study, the aim is to prepare polypropylene (PP)/serpentine composites and study their mechanical, thermal and morphological properties. Another objective is to explore whether it is possible to have PP/serpentine nanocomposites with melt intercalation method by using the advantage of the layer silicate structure of serpentine. The most widely used fillers in PP are talc and mica which belong to the phyllosilicates group of silicate minerals. So far, there has been almost no study employing serpentine as filler in either any polymers or PP, although it also belongs to the same group of minerals as talc and mica.
Accordingly, it was planned to divide the work into the study of two groups. In group 1, for the compositions with 2, 5, 10 and 20 wt% serpentine, the particulate filler effects of serpentine both alone and in the presence of surface treatments with hydrochloric acid (HCl) and silane coupling agent (SCA) were investigated. The most impressive results in terms of static and dynamic mechanical properties were achieved with SCA rather than HCl. When the effect of serpentine without
any treatment is considered, reinforcing effect of it can easily be observed without deteriorating the composite properties even at high filler loadings.
In group 2, the nanofiller effects of serpentine in 2 and 5 wt% filled compositions by modification of both the filler and the matrix were aimed to be examined with melt intercalation method. In addition to HCl and SCA treatments, maleic anhydride grafted polypropylene (PP-g-MA) and quaternary ammonium salt (QAS) of cetyl-trimethyl-ammonium bromide were used as compatibilizer and intercalating agent, respectively. While the amount of QAS was kept constant, different percentages of compatibilizer were employed. The presence of QAS and PP-g-MA further improved the properties with respect to group 1 members. Interestingly, the percentage strain at break values did not decrease as much as group 1 compositions with the same filler content. It can be concluded that partial intercalation of group 2 compositions was achieved, according to the X-ray and TEM results.
Keywords: Serpentine, PP/serpentine composites, SCA, PP-g-MA, serpentine nanocomposites
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Town, Christopher Albert. "Instream aeration of the Serpentine River." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26335.
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Urban encroachment and intensive agricultural pursuits within the Serpentine-Nicomekl watershed (in proximity to Vancouver, B.C.) have caused a number of serious fish kills on the Serpentine River since 1980. Low dissolved oxygen levels were responsible for these kills.
This study investigated some of the dynamic chemical and biological relationships within the river, as well as artificial aeration as a pollution abatement or in-situ improvement measure. Weekly sampling from July to December, 1985, inclusive, established a solid data base from which inciteful interrelationships were deduced. A strong correlation between chlorophyll-a and dissolved oxygen levels supported the hypothesis that, algae blooms dying in the Fall, create a massive oxygen demand. A prototype, (457 m) artificial aeration line was designed, installed and monitored to evaluate its potential for alleviating low dissolved oxygen conditions experienced in the Fall periods. The aeration system operated successfully during September, October and November of 1985; however, because of ideal weather conditions, dissolved oxygen levels never dropped below 7.3 mg/L, so the opportunity to evaluate in-situ oxygen transfer did not arise in 1985. Nevertheless, the data base generated supports the use of the prototype aeration unit as a means of "upgrading" a stretch of river subject to periodic, low, dissolved oxygen levels. Expansion of the system, to include other critical stretches of the Serpentine River, is strongly recommended.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
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Potts, Ian. "Particle Redistribution in Serpentine Engine Inlets." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595542100917769.
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Hughes, Ruth. "Serpentine tolerance in the Mimulus guttatus complex." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286489.
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Zhang, Lixin. "Dynamic analysis of viscoelastic serpentine belt drive systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0021/NQ45747.pdf.
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Laker, Travis S. "Secondary flows in a rotating serpentine circular duct." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/15898.
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Alvarez, Silva Mayeli. "Surface chemistry study on the pentlandite- serpentine system." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97112.
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Interaction with MgO-minerals is one mechanism suspected to reduce selectivity in flotation of pentlandite from ultramafic ore. Understanding the surface chemistry of the minerals involved will lead to improved flotation conditions that maximize flotation selectivity. The first part of the thesis compares isoelectric point (i.e.p.) and point of zero charge (p.z.c.) determined using Mular-Roberts [M-R] titration technique of MgO-minerals chlorite, serpentine and talc. The M-R technique was unsuccessful with talc, attributed to Mg2+ acting as potential determining ion. For serpentine and chlorite, respectively, p.z.c. was pH 4.3 and 4.6 and i.e.p. pH 3.2 and <3. Dispersion index (DI) for chlorite suggested that aggregation/dispersion is controlled by both; serpentine remained dispersed, possibly due to hydration effects.The second part determines surface properties of pentlandite and serpentine isolated from an ultramafic ore. Zeta potential measurements were made on minerals alone and as mixtures with either indifferent electrolyte or supernatant derived from an ore suspension as background. Individual mineral results anticipated interaction due to electrostatic attraction. This was confirmed in the mixed mineral case, with Mg(OH)2 precipitate interaction as an additional factor. Scanning electron microscopy validated the findings.Aggregation/dispersion was determined by turbidimetry using a light scattering technique and optical microscopy. The effect of selected factors on aggregation/dispersion of pentlandite and serpentine was investigated by a design of experiment (DOE). Concentration of carboxymethyl cellulose, CMC, and the interaction between CMC and pH were the important factors. Contact angle measurements explored effects of several factors on pentlandite hydrophobicity and, using a DOE, small-scale flotation was used to investigate effects on pentlandite floatability. The pH was the most important factor, acidic pH increasing both hydrophobicity and floatability. Copper activation enhanced both properties, as well; magnesium affected hydrophobicity at alkaline pH, but it did not show significant effect on floatability; serpentine was detrimental to the process; and CMC was capable of partially restoring the hydrophobicity and floatability of pentlandite depressed with serpentine.<br>L'interaction de la pentlandite avec des minéraux d'oxide de magnésium (MgO-) est soupçonnée d'être à l'origine de la sélectivité réduite de la pentlandite dans les procédés de flottation de minerais ultrabasiques. Une meilleure compréhension de la chimie de surface des minéraux impliqués devrait mener à l'amélioration des conditions de flottation qui en maximisent la sélectivité. La première partie de la thèse compare le point isoélectrique (p.i.e) et le point de charge nulle (p.c.n), déterminés à l'aide de la technique de titrage Mular-Roberts [M-R], de minéraux d'oxide de magnésium tels que la chlorite, la serpentine et le talc. Dans le cas du talc, la technique M-R a échoué, probablement dû aux ions Mg2+ qui jouent le rôle d'ions déterminateurs de potentiel. Dans le cas de la serpentine et de la chlorite, les p.c.n. ont été déterminés à pH 4,3 et 4,6 respectivement et les p.i.e à pH 3,2 et <3 respectivement. Des tests de décantations ont suggéré que l'agrégation/dispersion observée pour la chlorite était contrôlée à la fois par le p.c.n et le p.i.e ; la serpentine au contraire est restée dispersée, possiblement dû à des effets d'hydratation. La deuxième partie détermine les propriétés de surface de la pentlandite et de la serpentine isolées à partir d'un minerai ultrabasique. Des mesures du potentiel zêta ont été effectuées sur les minéraux seuls et mélangés en présence d'un électrolyte, indifférent dans un cas et surnageant dans l'autre cas, préparé à partir d'une suspension de minerai utilisée comme milieu d'étude. Les résultats relatifs aux minéraux individuels et en particulier les forces d'attraction électrostatique observables ont permis d'anticiper leur interaction. Cette hypothèse a été confirmée dans le cas des minéraux mélangés, étant après avoir pris en compte l'interaction de précipités de Mg(OH)2 comme facteur additionnel. Des observations au microscope électronique à balayage ont permis de valider les résultats. L'agrégation/dispersion a été déterminée par décantation en utilisant des techniques de lumière diffuse et de microscopie optique. L'effet de certains facteurs sur l'agrégation/dispersion de la pentlandite et de la serpentine a été étudié sur la base d'un plan d'expériences (PE). Entre autres, la concentration en carboxymethyl cellulose (CMC) et l'interaction entre le CMC et le pH ont été considérés comme des facteurs importants. Des mesures d'angle de contact ont permis d'explorer l'hydrophobicité de la pentlandite et, à l'aide d'un PE, une étude de flottation à petite échelle a été réalisée pour investiguer la flottabilité de la pentlandite. Les résultats ont montrés que le pH était le facteur le plus important, un pH acide ayant pour effet d'augmenter à la fois l'hydrophobicité et la flottabilité. L'ajout de cuivre a également permis de renforcer ces deux propriétés par un effet d'activation; la présence de magnésium au contraire a affecté l'hydrophobicité de la pentlandite à pH alcalin mais n'a pas eu d'effet significatif sur ses propriétés de flottabilité; la présence de serpentine s'est trouvée être préjudiciable au procédé mais l'utilisation de CMC a pu être utilisée afin de restaurer partiellement l'hydrophobicité et la flottabilité de la pentlandite diminuées par la présence de la serpentine.