Dissertations / Theses on the topic 'Zinc sulphate'
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Lo, Nigel. "Crystallization of gypsum in zinc sulphate solution." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20507.
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The purpose of this research is to use a mathematical model to study the removal of calcium in the form of gypsum from zinc sulphate solution by cooling from 80ºC to 30ºC in a batch crystallizer. Factors such as cooling-rates, initial solution composition, and seed amount are analyzed. Using the simulation module developed, it is found that the removal of calcium can be improved by operating at a high temperature, which speeds up both the growth and nucleation kinetics, and produces a higher supersaturation by lowering the equilibrium molality of calcium ion in solution. Also, the addition of seed can reduce the activation energy requirement for nucleation by providing favourable surface for the formation of nuclei and enhance crystallization. Finally, experiments are performed to see if the results qualitatively support the simulation findings.
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Lo, Nigel. "Crystallization of gypsum in zinc sulphate solution." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ44024.pdf.
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Cheng, Terry Chi-Ming 1968. "Production of hematite in acidic zinc sulphate media." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38169.
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In this work, the kinetic and equilibrium profiles of each individual reaction step involved in the production of hematite at 200°C via oxydrolysis of ferrous sulphate in concentrated zinc sulphate media were established. Crystallization of ferrous sulphate was found to play a crucial role in the overall process due to its relatively low solubility and fast crystallization kinetics at elevated temperatures. In fact, the overall kinetics of the oxydrolysis process were found to be limited by the re-dissolution of ferrous sulphate. Pre-crystallization of ferrous sulphate prior to oxidation was found to result in enhanced overall kinetics, cutting down the required retention time from 3 to 2 hours. Enhanced kinetics were also achieved by performing oxydrolysis in two-temperature stages: a low temperature (T = 180°C) first stage with retention time >20 min and an elevated temperature (T = 200°C) second stage with retention time >100 min.The typical composition of the hematite material produced in this work was 64.3% Fe, 1.3% S (as SO4), 0.6% Zn, and 4.6% H2O. The sulphur content was found to be predominantly (0.6--0.8%) due to formation of sodium jarosite with the remaining (0.3--0.5%) attributed to SO4 chemisorption, and (to less extent) basic ferric sulphate formation. In the absence of zinc sulphate, the majority of sulphate contamination was due to basic ferric sulphate formation. Hematite was found to form via a predominantly homogeneous nucleation mechanism with sub-micron crystallites clustered together as aggregates of 5--10 mum size and around 7 m 2/g specific surface area. In contrast, hematite produced by direct hydrolysis of ferric sulphate possessed one order of magnitude higher specific surface area. As for the industrial hematite product, its composition was found to be 52.6% Fe, 4.6% S, 1.0% Zn, and 8.8% H2O. The sulphur contamination in the industrial product was mainly due to co-precipitation of jarosite and basic ferric sulphate compounds. Hydrothermal trans-formation of the industrial hematite product at elevated temperatures (>200°C) and retention time of >60 min with solids loading as high as 16 wt.% proved to be effective in reducing the sulphur content to less than 1%.
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Principe, Frank T. "Separation of iron(III) from zinc sulphate-sulphuric acid solutions using organophosphoric acid extractants." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0016/MQ55025.pdf.
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Pemmaraju, Prajyula. "Zinc Silicate Based Pigments for Corrosion Inhibition of Cold Rolled Steel." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1552657123301627.
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Ménard, Vincent. "Controlled oxidative precipitation of manganese from an industrial zinc sulphate solution using a sulphur dioxide and oxygen gas mixture." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82618.
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The purpose of the present work was to remove selectively manganese from a neutral leach zinc-rich solution at 80ºC using the gas mixture of sulphur dioxide (SO2) and oxygen (O2) as oxidizing agent. In order to determine the optimum conditions for manganese removal using SO 2/O2, several semi-batch experiments were performed, where the effects of pH, ORP, SO2/O2 ratio, mixing intensity, etc. were investigated. Results of these tests showed that SO2/O 2 was a fast and effective oxidant for removing manganese down to ppm level provided that the appropriate reactor design, agitation and SO 2/O2 ratio were employed. In an attempt to improve the precipitate's characteristics, e.g. crystallinity and solid/liquid separation, a new technique called Step-Wise Oxidative Precipitation (S.W.O.P) was investigated using a two-reactor continuous circuit employing pH and ORP control and precipitate recycling. These tests revealed that a birnessite-like phase with general formula (Na0.7Ca0.3)Mn7O14·2.8H 2O was produced with co-precipitation of a significant amount of zinc apparently via substitution. The applied technique (S.W.O.P combined with recycling) proved effective in producing dense particles but not on lowering zinc losses. The biggest advantage of this novel oxidation technique was the total elimination of scaling. (Abstract shortened by UMI.)
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Akey, D. H., H. M. Flint, and J. R. Mauney. "Application of Zinc Chelate and Ammonium Sulphate Supplements: Increased Damange to Cotton Foliage from Beet Armyworm and Cabbage Looper." College of Agriculture, University of Arizona (Tucson, AZ), 1989. http://hdl.handle.net/10150/204844.
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Foliar applications of zinc as a chelate or sulphate with ammonium sulphate to plots of cotton resulted in beet armyworm infestations with leaf damage that was 2.3 to 3.1 times greater than that in control plots.
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Kladova, Anna Vadymivna. "Metals in proteins from sulphate-reducing bacteria: adenylate kinase and ATP sulfurylase. Proteins containing cobalt, zinc, iron (II) ions." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2009. http://hdl.handle.net/10362/6342.
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A Thesis submitted at the Faculty Science and
Technology of the New University of Lisbon for a degree in Doctor of Philosophy in Biochemistry with specialization in Physical Biochemistry(fellowship BD SFRH/BD/24744/05)- Foundation for Science and Technology
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Salih, Baraah. "A comparative study of immunofluorescence, zinc sulphate centrifugal flotation and FASTest®GIARDIA strip for detection of Giardia in dogs and cats." Thesis, Uppsala universitet, Institutionen för kvinnors och barns hälsa, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-357635.
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Giardia intestinalis is the most common parasite found in dogs and cats. It is traditionally diagnosed using a microscope. These methods include direct immunofluorescence, DIF, and zinc sulphate centrifugal flotation, ZnSO4 C-flotation. However, there are commercially available SNAP tests such as the FASTest® GIARDIA strip that is often used by dogs and cats owner to detect Giardia. The aim of this study was to compare the sensitivity, cost and labor intensity of these three methods for detection of Giardia. To investigate this, 150 samples from dogs and cats were examined at the National Veterinary Institute in Sweden. The samples were a mixture of diarrheic and non-diarrheic stool. Of the 150 stool samples 100 samples were examined with FASTest® GIARDIA strip while 150 samples were examined with DIF and ZnSO4 C-flotation. The results indicated that FASTest® GIARDIA strip had a sensitivity of 66.18 %, a cost of 100 Swedish crowns (SEK) per sample and was the easiest test to use. ZnSO4 C-flotation had a sensitivity of 89.90 %, cost 418.75 SEK and took about 15 minutes to perform. DIF had 100 % sensitivity and specificity and due to that it was used as a standard reference method. The cost for DIF was 300 SEK and took more than an hour to perform per sample. The conclusion from this study is that, FASTest® GIARDIA strip is not a recommended test for detection of Giardia despite their low cost and easiness to use. DIF and ZnSO4 C-flotation remain a better diagnostic option for detection of Giardia.
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Bouregaya, Souad. "Synthèse d'un ciment alitique à moindre impact environnemental à partir de vase de barrage et utilisant le sulfate de zinc comme minéralisateur." Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0026/document.
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L’objectif de cette étude est de réaliser la synthèse d’un ciment riche en phases réactives, obtenu par cuisson à une température inférieure ou égale à 1300°C d’un cru constitué de vase de barrage et d’un complément de chaux et utilisant du sulfate de zinc comme minéralisateur. Cette étude donne les caractéristiques minéralogiques et les propriétés physico- mécaniques du ciment synthétisé. L’analyse qualitative et quantitative par diffraction des rayons X a été utilisée pour caractériser les matériaux bruts et les minéraux du ciment. L’évolution du durcissement des pâtes de ce ciment a été suivie et quantifiée par calorimétrie isotherme, DTG, diffraction des rayons X et au moyen d’essais mécaniques en compression sur éprouvettes de pâte pure. Les résistances obtenues à 7 et 28 jours permettent de viser une classification CEM II 32,5 NThe objective of this study is the synthesis of a cement rich in reactive phases, obtained by burning, at a temperature lower than or equal to 1300 °C, a raw material composed of sludge from a dam with a complement of lime, and using zinc sulphate as a mineralizer. This study gives the mineralogical, physical and mechanical characteristics and properties of the synthesized cement. Qualitative and quantitative X-ray diffraction analysis was used to characterize the raw materials and the minerals of the cement. The evolution of its hardening was monitored and quantified by isothermal calorimetry, DTG, X-ray diffraction and mechanical compression tests on pure paste samples. The strengths obtained at 7 and 28 days make it possible to aim at a CEM II 32.5 N classification
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Kumar, Bhaskar. "ZINC CADMIUM SULPHIDE AND ZINC SULPHIDE AS ALTERNATIVE HETEROJUNCTION PARTNERS FOR CIGS2 SOLAR CELLS." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4052.
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Devices with ZnCdS/ZnS heterojunction partner layer have shown better blue photon response due to higher band gap of these compounds as compared to devices with CdS heterojunction partner layer. CdS heterojunction partner layer has shown high photovoltaic conversion efficiencies with CIGS absorber layer while efficiencies are lower with CuIn1-xGaxS2 (CIGS2). A negative conduction band offset has been observed for CdS/CIGS2 as compared to near flat conduction band alignment in case of CdS/CIGS devices, which results in higher interface dominated recombination. Moreover, it has been predicted that optimum band offsets for higher efficiency solar cells may be achieved for cells with alternative heterojunction partner such as ZnS. With varying ratio of Zn/ (Zn+Cd) in ZnxCd1-xS a range of bandgap energies can be obtained and thus an optimum band offset can be engineered. For reducing interface dominated recombination better lattice match between absorber and heterojunction partners is desirable. Although CdS has better lattice match with CuIn1-xGaxS2 absorber layer, same is not true for CuIn1-xGaxS2 absorber layers. Utilizing ZnxCd1-xS as heterojunction partner provides a range of lattice constant (between aZnS= ~5.4 Ǻ and aCdS= ~5.7 Ǻ) depending on Zn/(Zn+Cd). Therefore better lattice match can be obtained between heterojunction partner and absorber layer. Better lattice match will lead to lower interface dominated recombination, hence higher open circuit voltages. In the present study chemical bath deposition parameters are near optimized for high efficiency CIGS2 Solar cells. Effect of various chemical bath deposition parameters on device performance was studied and attempts were made to optimize the deposition parameters in order to improve the device performance.In/(In+Ga) ratio in absorber layer is varied to obtain good lattice match and optimum band alignment. Solar cells with conversion efficiencies comparable to conventional CdS/CIGS2 has been obtained with ZnxCd1-xS /CIGS2. High short current as well as higher open circuit voltages were obtained with ZnxCd1-xS as alternative heterojunction partner for CIGS2 solar cells as compared to SLG/Mo/CIGS2/ CdS / i-ZnO/ZnO:Al.M.S.M.S.E.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr MSMSE
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Khai, Nguyen Manh. "Effects of using wastewater and biosolids as nutrient sources on accumulation and behaviour of trace metals in Vietnamese soils /." Uppsala : Dept. of Soil Sciences, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200774.pdf.
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Wakeham, Steve. "Protective, antireflection coatings for multispectral zinc sulphide." Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402630.
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Harzali, Hassen. "Cristallisation de ZnSO4,7H2O sous ultrasons : Étude expérimentale et étude microscopique." Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0038/document.
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La cristallisation assistée par ultrasons permet de diminuer le temps d'induction et la largeur de la zone métastable, de modifier la distribution de tailles, de modifier le faciès des cristaux et d'augmenter le nombre des cristaux formés. L'origine microscopique de cet effet reste à ce jour non élucidée. Les ultrasons de puissance engendrent dans un liquide la naissance et l'oscillation très violente de milliards de petites bulles de gaz, phénomène appelé cavitation. Le cycle d'une de ces bulles sur une période acoustique consiste en une phase explosive suivie d'une implosion violente. A la fin de l'implosion, la pression peut atteindre 1 GPa. Plusieurs hypothèses sur les mécanismes mis en jeu sont proposées dans la littérature : refroidissement de la solution et augmentation de la pression au voisinage de l'interface, évaporation du solvant dans la bulle, et ségrégation des molécules ou des ions du soluté au voisinage de la bulle lors de la phase implosive. Afin d'examiner l'influence de la pression, des expériences de cristallisation du sulfate de zinc heptahydraté ont été menées (mesure de temps d'induction). Ce sel présente une solubilité indépendante de la pression entre 0 et 10 000 bars. Nos expériences ont montré que le temps d'induction est fortement diminué en présence d'ultrasons. Ce résultat nous permet d'affirmer que la pression au voisinage de la bulle n'entre pas en jeu dans le mécanisme de la nucléation primaire du ZnSO4,7H2O en présence d'ultrasons. Après l'étude de l'effet de la sursaturation, nous avons essayé d'exploré l'effet de la puissance ultrasonore, du gaz dissous et de la hauteur du liquide dans la cuve sur le temps d'induction. Il a été constaté que les ultrasons permettent de diminuer le temps d'induction. Il a été observé que la courbe du temps d'induction en fonction de la hauteur de la solution présente un minimum. Un autre volet de cette thèse réservé à la modélisation et la simulation. Dans un premier temps, la concentration en clusters ou agrégats moléculaires au voisinage de la bulle été calculée dans le cas du ZnSO4,7H2O grâce à la théorie de la ségrégation en fonction de la pression acoustique. La simulation montre qu'il y a une sur-concentration des clusters (jusqu'à 25 fois supérieure à la concentration stationnaire) augmentant ainsi la probabilité de contact des clusters, durant un temps très court, pouvant ainsi modifier le processus global de nucléation. Dans un deuxième temps, la modélisation/simulation de l'acoustique par COMSOL est réalisée en vue de déterminer les résonances de notre système (liquide + parois de la cuve). Les résonances observées sont cohérentes avec les mesures de temps d'inductionPower ultrasound is known to enhance crystals nucleation, and nucleation times can be reduced by oneup to three orders of magnitude for several organic or inorganic crystals. The precise physics involved in this phenomenon still remains unclear, and various mechanisms involving the action of inertial cavitation bubbles have been proposed. In this paper, two of these mechanisms, pressure and ségrégation effects, are examined. The first one concerns the variations of supersaturation induced by the high pressures appearing in the neighbourhood of a collapsing bubble, and the second one results from the modification of clusters distribution in the vicinity of bubble. Crystallisation experiments were performed on zinc sulphate heptahydrate ZnSO4. 7H2O, which has been chosen for its pressure-independent solubility, so that pressure variations have no effect on supersaturation. As observed in past studies on other species, induction times were found lower under insonification than under silent conditions at low supersaturations, which casts some doubts on a pure pressure effect. The interfacial energy between the solid and the solution was estimated from induction times obtained in silent conditions, and, using classical nucléation theory, the steady-state distribution of the clusters was calculated. Segregation theory was then applied to calculate the over-concentrations of n-sized clusters at the end of the collapse of a 4 lmbubble driven at 20 kHz by different acoustic pressures. The over-concentration of clusters close to the critical size near a collapsing bubble was found to reach more than one order of magnitude, which may favour the direct attachment process between such clusters, and enhance the global nucleation kinetics. The effects of acoustic cavitation on crystallization of ZnSO4. 7H2O was observed in a sono-reactor build-up from a large emitting area transducer located at the bottom of the vessel. The experimental results have shown that the dissipated acoustic power passes through a maximum at about 15±1 cm, and that the induction-time passes through a minimum for the same liquid-level. The dissipated-power and the induction-time are found to be well correlated as the liquid height was varied. The acoustics of the sono-reactor was studied with linear acoustics, accounting for the wall vibrations by using the COMSOL software. Theoretical dissipated acoustic powers were compared to the experimental ones
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Ahmed, Shibbir. "Cadmium sulphide / Zinc sulphide quantum dot decoration of three-dimensional porous graphene." Thesis, Umeå universitet, Institutionen för fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-94348.
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Moradi, Saeid. "Hydrometallurgical processing of mixed sulphite-oxide lead and zinc ores." Thesis, Imperial College London, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549712.
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Mixed sulphide-oxide lead and zinc ores are most often found in the transition, and occasionally in the oxidised, zones of lead-zinc ore bodies. They are of great importance because there are numerous unexploited or abandoned reserves of these ores in the world. However, they present difficulties for conventional mineral processing due to complex mineralogy. In this thesis, the specific problems associated with these types of ores are described and methods for solving these problems, combining economic and technical considerations, are discussed. The results of experiments carried out at laboratory scale are presented, in which the dissolution of a mixed ore sample from the Angouran mine in Iran in sulphuric acid in the absence of oxidants and also the dissolution of the sulphide part of sample in ferric sulphate-sulphuric acid solutions in the absence and presence of other oxidants, i.e. oxygen, potassium permanganate, manganese dioxide and hydrogen peroxide. Fractional factorial experimental designs were used to determine which variables are significant and understand how these variables interact and drive the dissolution processes. Mathematical models are derived from the statistical analyses of the results. The kinetic studies indicate the rate controlling steps in non-oxidative and oxidative leaching are: diffusion of products back to the exterior surface of oxidised zinc minerals, and diffusion of ferric ions through the layer of elemental sulphur surrounding the sphalerite particles to the surface of the unreacted core of sphalerite particles, respectively. The dissolution of significant minerals in the ore sample, i.e. smithsonite, hemimorphite, sphalerite, cerussite, mimetite and kehoite during non-oxidative and oxidative leaching at optimal conditions were investigated by the XRD method. The results show the feasibility of zinc recovery from mixed sulphide-oxide lead and zinc ores, which underlines the potential of this approach. A conceptual flow diagram for the hydrometallurgical processing of these ores is proposed.
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Sitoka, Stefanus. "Exploration status for oxide and sulphide zinc ores at Skorpion Zinc Mine, Namibia." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1018204.
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The thesis is inspired by recent interests in oxide zinc ores caused by new developments in the technology of hydrometallurgy. The improved techniques turned the non-sulphide zinc ores in to attractive exploration targets due to a number of advantages such as low metal recovery costs and favorable environmental aspects such as the obvious absence of sulfur (Large, 2001). Historically extraction of zinc metal from oxide ores was not possible until recently. The metallurgical complexity resulted in a lack of interest and hence some economic oxide zinc ores might have been missed by conventional exploration techniques. The study presents a review of exploration status at Skorpion mine based on different exploration techniques and their application to sulphide and oxide zinc ore exploration. The challenge facing the mineral exploration industry today is the inability to detect mineral deposits under cover. Therefore a key to successful exploration program lies in the selection of the right exploration technique. Important parameters that should be highlighted in the exploration methodology are the geological situation of an area, equipment applicability and effectiveness, survey limitation, equipment mobilization and the safety aspects involved. The aim of this thesis is to provide a general guideline for sulphide and non-sulphide zinc ore exploration on the Skorpion area and other similar geological environments. Geochemical surveys appears to be more complimentary in exploration of non-sulphide zinc exploration. Although geochemical techniques are preferred, it is equally important to choose the right soil horizon. Furthermore, sample media may mean the difference between success and failure in geochemical exploration of non-sulphide zinc mineralization, due to high mobility of zinc in the surficial environment. On cost comparison, surface geochemical surveys programs are more cost effective except for litho-geochemical sampling which are commonly carried out through subsurface drilling. Geophysical techniques have limited application in exploration of non-sulphide zinc mineralization due to a lack of major physical properties (e.g., magnetic and electrical properties) in non-sulphides unlike their sulphide counterparts. However geophysical methods are commendable in delineating massive and disseminated sulphides mainly if they are associated with major Fe minerals (pyrrhotite or magnetite). In addition, geophysical techniques may be effective in mapping of subsurface primary and secondary structures such as basin faults which might have acted as pathways for metal-rich fluids. Terms non-sulphide and oxide zinc mineralization are used interchangeably throughout the thesis. Recommendations on regional and local target generation are presented in the thesis to give some basic guide lines on target generation strategies. The most important conclusion reached in this study is that, success in exploration for non-sulphide or sulphide zinc mineralization might be enhanced through the integrated exploration methodology.
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Doherty, Stephen. "The photochemistry and photophysics of colloidal dipsersions of zinc sulphide and cadmium sulphide." Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306053.
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The potential use of colloidal semiconductor systems regarding solar energy conversion and preparative organic chemistry has long been recognised. However there have been few reports concerning the characterisation of semiconductor systems with a view to identifying the factors which affect semiconductor photocatalysis. This thesis identifies the main criteria which control energy ttansfer from the semiconductor excited state to an acceptor molecule. 1bese factors are: degradation (the semiconductor must be stable under photolysis conditions). thermodynamics (charge ttansfer from the semiconductor excited state to the acceptor ground state must be exothermic). kinetics (long lived semiconductor excited states favour energy ttansfer) and physical (charge transfer generally requires intimate contact between the donor/acceptor species). In order to satisfy these conditions ZnS. CdS and ZnS/CdS semiconductors have been prepared in iPAJwa~. AOT/heptane!water and water. Together. these systems provide three distinct phases for additive dissolution (i.e. water. iPA, heptane). UV/VIS absorption spectroscopy has been used to detennine the absorption onset positions of the colloids. From these measurements it has been found that the CdS, ZnS and CdSlLnS systems have absorption onset energies ranging from 2.53 to 4.96 eV which are dependent on the semiconductor particle sizes. Importantly, co-colloidal CdSlLnS systems have been prepared which have tuneable absorption onset energies (2.53 to 4.96 eV). Furthermore. the AOT !heptane/water systems show indefinite stability to dark ageing. Photolysis experiments (l = 254 nm) have revealed that semiconductor photodegradation shows a marked oxygen dependence and can be inhibited by the presence of charge scavengers (e.g. S2-. isopropanol) illustrating the importance of surface reactions. These results led to the development of semiconductor systems which had photodegradation quantum yields of zero. Time-resolved and steady state measurements have proven that semiconductors luminesce with high quantum yields (~ > 0.1), via an "allowed" process, over nanosecond time scales. The luminescence excitation spectra show the characteristic semiconductor absorption profile. The semiconductors give a broad emission band (1.91 to 3.4 eV) which is Stokes shifted from the absorption profile (by up to 0.9 eV). The importance of surface sites has been demonstrated and the main non-radiative (e.g. M-aqua and M-S042-) and radiative centres (M2+, S2-) have been identified. It has been found that luminescence quenching by additives is a powerful indicator for energy ttansfer processes. The results from iP A quenching experiments led to the photochemistry of CdS and ZnS in iP Nwaaer being investigated. Upon illumination of both of these systems (A = 254 nm; a wavelength at which iPA does not absorb) acetone was produced with a concomitant reduction in the iPA concentration (measured using IH and 13C NMR). Finally, new models have been proposed for the "exciton" absorption, photodegradation and photoluminescence of conoidal semiconductor systems
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Boudghene, Stambouli Amine. "Degradation mechanism in zinc sulphide/manganese electroluminescent displays." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328389.
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Macken, Declan. "Manganese doped zinc sulphide as an electroluminescent phosphor." Thesis, University of Ulster, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357619.
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Holgate, Sharon Ann. "Luminescence studies of fluorides, glasses and zinc sulphide." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321469.
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Barrioz, Vincent. "Laser-fibre system for in-situ stress monitoring of thin films." Thesis, Bangor University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273632.
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Fuls, Herman Franz. "Evaluation of processing options for the treatment of zinc sulphide concentrates at Skorpion zinc." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10497.
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Includes bibliographical references (p.84-87).The zinc oxide resource of Skorpion Zinc, an integrated zinc mine and refinery, near Rosh Pinah in southern Namibia, will be depleted by end of 2015 with a possible extension to 2017. Extensive exploration drilling was unsuccessful. With the abundant availability of zinc sulphide concentrates regionally the life of the operation may be extended by processing these concentrates. The leach kinetics of zinc sulphides is vastly slower than oxides, preventing the processing of zinc sulphides using the existing process, under current conditions. The challenge is to identify a suitable zinc sulphide treatment process that can be integrated with the existing plant. Information from the bench scale test work and an update of the economic models will provide sufficient accuracy for Skorpion to select either the pressure or the atmospheric leach process.
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Liddell, I. T. "Thermoluminescence of single crystal of calcium and zinc sulphide." Thesis, Robert Gordon University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380742.
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Kärner, Katrin. "The metallogenesis of the Skorpion non-sulphide zinc deposit, Namibia." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=985497890.
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Lawrie, Catriona H. "Study of the reaction between hydrogen sulphide and zinc oxide." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/11041.
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Experiments were conducted to study the absorption reaction of hydrogen sulphide with zinc oxide forming zinc sulphide and water. The reaction is of commercial importance for the removal of hydrogen sulphide from reactor feed streams and from natural gas. Most of the experiments were performed on a commercial ICI zinc oxide-based absorbent prepared by calcination of basic zinc carbonate but a number of experiments were also performed on samples of basic zinc carbonate or of zinc oxide prepared by different treatments. The reactions were carried out in a shallow bed flow reactor containing 0.2-0.6g of absorbent at a pressure just above atmospheric and at temperatures in the range 0 to 450C. Feed gases containing 0.06-0.7% v/v hydrogen sulphide and 0-0.5% v/v water in nitrogen were used. On-line gaseuos analysis was performed using a Thermal Conductivity Detector with complementary information provided by sulphur analysis and electron microprobe analysis of the discharged partially sulphided absorbent. The specific reaction rate was observed to be very high initially but to decline to a much slower pseudo-steady state (pss) rate. The pattern of this decline was found to be a function of particle size, with larger particles exhibiting slower, diffusion-limited rates in the initial period but higher pss rates than smaller particles. This latter result was attributed to an enhanced water concentration in the centre of larger particles. Microprobe analysis indicated uniform sulphiding at about 20% absorbent conversion whereas at low conversions an outer sulphided shell surrounds a central unreacted core. The conversion of the absorbent at pss (in the range 9-23%) was observed to increase with increasing partial pressures of water and of hydrogen sulphide in the feed. A marked dependence of the pss rate upon water partial pressure and a decrease in the rate with increasing temperature were observed and interpreted as indicative of an autocatalytic reaction. The role of water in facilitating solid rearrangement is consistent with the results of interrupted experiments which showed enhanced water adsorption and reaction rate after isolation. The pss rate was found to be insensitive to hydrogen sulphide concentration in the range studied. There appears to be an optimal calcination temperature of the absorbent precursor although this may not correspond with the temperature yielding maximal specific surface area. The effects of some impurities in the commercial absorbent were also investigated.
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Lo, Wai Hung. "Temperature effect on the composition and the growth of Cadmium zinc sulphide alloy, CdxZn₁-xS." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174854a.pdf.
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Thesis (M.Sc.)--City University of Hong Kong, 2005.At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. On t.p. the "x" of "CdxZn₁-xS" are subscript. Title from title screen (viewed on Sept. 4, 2006) Includes bibliographical references.
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Shen, Xiu-Li. "Chemical beam epitaxial growth of (001) ZnS." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/18896.
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Sands, D. "Growth and characterisation of thin films of zinc sulphide on silicon." Thesis, University of Bradford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379798.
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McLaughlin, J. "Investigation of thin film properties of luminescent manganese doped zinc sulphide." Thesis, University of Ulster, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282979.
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Jönsson, Jörgen. "Phase transformation and surface chemistry of secondary iron minerals formed from acid mine drainage." Doctoral thesis, Umeå University, Chemistry, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-156.
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The mining of sulphidic ore to extract metals such as zinc and copper produces huge quantities of waste material. The weathering and oxidation of the waste produces what is commonly known as Acid Mine Drainage (AMD), a dilute sulphuric acid rich in Fe(II) and heavy metals. This thesis serves to summarise five papers reporting how the precipitation of Fe(III) phases can attenuate the contamination of heavy metals by adsorption processes.
Schwertmannite (Fe8O8(OH)6SO4) is a common Fe(III) mineral precipitating in AMD environments at pH 3-4. The stability and surface chemistry of this mineral was investigated. It was shown that the stability depended strongly on pH and temperature, an increase in either promoted transformation to goethite (α-FeOOH). Two pH dependent surface species of SO42- were detected with infrared (ATR-FTIR) spectroscopy.
The adsorption of Cu(II), Pb(II) and Zn(II) to schwertmannite occurred at lower pH than to goethite, whereas Cd(II) adsorption occurred in a similar pH range on both schwertmannite and goethite. Extended x-ray absorption fine structure (EXAFS) spectroscopy suggests two surface species for Cu(II) and Cd(II) at the schwertmannite surface. Cu(II) adsorbs monodentately and Cd(II) bridging bidentately to adsorbed SO42-. Both metal ions also adsorb in a bridging bidentate mode to the surface hydroxyl groups. At pH 7.5 up to 2.7 μmol Cd(II) m-2 could be adsorbed to schwertmannite, indicating a large adsorption capacity for this mineral.
The acid-base properties of two NOM samples were characterised and could be well described as diprotic acids below pH 6. The adsorption of NOM to schwertmannite and goethite was very similar and adsorption occured in a very wide pH range.
High concentrations of NOM increased the adsorption of Cu(II) to goethite at low pH whereas a slight decrease was noted at low concentrations of NOM. No effect was detected in the schwertmannite system.
The formation of Fe(III) phases from precipitation of AMD was shown to be very pH dependent. At pH 5.5 a mixture of minerals, including schwertmannite, formed whereas at pH 7 only lepidocrocite (γ-FeOOH) formed. The concentration of Zn(II) in AMD could by adsorption/coprecipitation be reduced to environmentally acceptable levels.
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Ma, Jun. "The deposition and electro-optical properties of thin film zinc sulphide phosphors." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388877.
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Lee, King Hung. "Ellipsometric studies of the nucleation of zinc sulphide films in ultra-high vacuum." Thesis, Queen's University Belfast, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335519.
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CORTEZ, ORFELINDA AVALO. "FLUID DYNAMICS AND KINETICS STUDY OF ZINC SULPHIDE CONCENTRATES ROASTING IN FLUIDIZED BED REACTOR." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3839@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICONo presente trabalho apresenta-se um estudo fluido dinâmico e cinético da ustulação de um concentrado de sulfeto de zinco a 950 Graus Celsius. Os resultados foram coletados na literatura para experimentos realizados em um reator de leito fluidizado industrial com enriquecimento do ar com oxigênio. A caracterização teórica e experimental foi realizada com as variáveis operacionais de reatores industriais. Foram levantados diagramas fluido dinâmicos teóricos (Geldart, Schytill e Grace) para a prática industrial em condições específicas. Foi observado que mudanças na temperatura, diâmetro médio da partícula, velocidade superficial do gás e tamanho do reator afetam as fronteiras dos diagramas. Os programas para caracterizar o comportamento do leito do reator foram escritos no Mathcad. Um estudo cinético foi realizado para avaliar as influências dos parâmetros temperatura, pressão parcial de O2, tamanho da partícula, massa específica da partícula e do gás fluidizante e viscosidade do gás sobre a conversão de ZnS a ZnO. Os resultados mostraram que o enriquecimento do ar com oxigênio é uma alternativa recomendável para o aumento da eficiência da conversão de concentrados de ZnS em reatores de leito fluidizado.
This work presents a fluid dynamics and kinetics study of the roasting of zinc sulphide concentrates at 950 Celsius Degrees. The data were collected in the literature for experiments carried out in an industrial fluidised bed reactor with an excess of oxygen. The theoretical and experimental characterisation was conducted with the operating variables of the industrial reactor. Theoretical fluid dynamic diagrams (Geldart, Schytill and Grace) were drawn for the industrial practice at certain conditions. It was observed that, with changing temperature, mean particle diameter, gas superficial velocity and reactor size, the boundaries of the diagrams were affected. Mathcad programs to characterise the bed behaviour are presented. The kinetics was studied to evaluate the influences of the following parameters: temperature, O2 partial pressure, particle size, gas and particle densities, and gas viscosity on the conversion of ZnS to ZnO. The results effectively demonstrate that, for the oxygen enrichment employed, the conversions increased in approximately 15 percent. Therefore, the oxygen enrichment is an advisable alternative to increase the efficiency of ZnS concentrates roasting in fluidised bed reactors.
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Saidin, Mohamad Khairi B. "The properties of mixed crystals of zinc-cadmium-sulphide(Zn(_x)Cd(_1-x)S)." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6814/.
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CdS and ZnS are two binary compounds of II-VI semiconductors which form a continuous series of solid solutionsthroughout the whole range of composition (Zn(_x)Cd(_1-x)S). The main purpose of the work reported in this thesis was to characterise some electrical properties of Zn(_x)Cd(_1-x)S crystals grown in the department. Atomic Absorption Spectroscopy (AAS) was used to determine the actual composition of the solid solutions to compare with Energy Dispersive Analysis by X-Ray (EDAX) measurements. A calibration curve of ratio intensity versus composition can then be used to estimate thecomposition the X-Ray of Zn x Cdl -x S diffraction non-destructively. From the x-ray diffraction studies, all Zn(_x)Cd(_1-x)S crystals with x<0.85 were found to have the hexagonal, wurtzite form while ZnS crystals have the cubic, zinc blende phase. Conductivity and Hall coefficient measurements were also carried out. At 300K, conductivities up to about lxl0(^-1) ohm(^-1)cm(^-1) could be achieved for composition up to x=0.45. The Hall mobility was found to decrease drastically at x=0.2. Scattering due to a combination ofpolar optical and piezoelectric processes was thought to Control the carrier mobility for crystals with x<0.2. With x>0.2, scattering due to ionised impurities, space charge or alloy processes is probably more important. The barrier heights of Au-Zn(_x)Cd(_1-x)S (x<0.5) Schottky diodes were calculated from forward I-V characteristics, C-V and photoelectric measurements were also carried out. A quite linear relationship with composition was observed for barrier heights measured by photoelectric method. Barrier heights calculated by the other methods was very much dependent on the nature of the barrier. From steady state photo capacitance studies, a level situated at about l.l-1.2eV above the valence band is the dominant feature for copper doped samples and crystals grown by the Piper-Polich method. This centre was pinned to the valence band. A second deep centre situated at about 1.4-1.5eV below the conduction band was also observed in some samples and was pinned to the conduction band. The existence of this centre is thought to depend very much on the history of the individual sample.
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Hack, L. A. "Development and validation of the marine benthic copepod Robertsonia propinqua as a bioindicator to monitor estuarine environmental health." Lincoln University, 2008. http://hdl.handle.net/10182/307.
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Studies in the USA have reported that species of meiobenthic copepods can be used as bioindicators of sediment-associated contaminants. The main objective of this research project was to develop and validate methods to assess the effects of estuarine pollution, using the marine benthic copepod Robertsonia propinqua as a bioindicator of environmental health in New Zealand intertidal / estuarine areas. Cultures of R. propinqua were set up and maintained in the laboratory and individuals used in 96h acute and full life-cycle chronic bioassays using the pre-selected contaminants atrazine and zinc sulphate. From the 96h acute experiments it was found that the lethal doses at which 50% mortality occurred (LC50) for exposed nauplii and adult individuals were 7.5 mg/L and 31.8 mg/L, respectively for atrazine and 1.7 mg/L and 2.7 mg/L, respectively for zinc sulphate. This indicated that the nauplii life stage was more sensitive than were the adult life stages for exposure to both contaminants. Based on the 'trigger' values reported (atrazine = 0.013 mg/L, zinc = 0.015 mg/L) in the Australian and New Zealand guidelines for fresh and marine water quality, which provide values at which concentrations of contaminants can occur in the environment before they begin causing effects on aquatic fauna, it is unlikely that the calculated LC50s in the current research will induce biological effects in exposed copepods in the short-term. The calculated LC50 results were then used to further investigate the effects of chronic exposure of sediment-associated contaminants on the complete life-cycle (egg-reproductive adult) of R. propinqua. In a laboratory-based full life-cycle toxicity test, field-collected sediments from polluted sites in the Auckland and Bay of Plenty regions reduced reproductive output (nauplii and copepodite production) of R. propinqua individuals, but the number of males and females, gravid females, clutch size per female and the number of eggs produced were not affected by either the polluted or non-polluted (reference) sediment samples from both field regions. Field investigations of meiofauna community composition in polluted and non-polluted field sites were carried out in 2004 in the Auckland and Bay of Plenty field regions in New Zealand. Greater sediment organic content and a correspondingly deeper redox potential discontinuity layer occurred in all polluted field sites compared with the non-polluted sites. However, species composition could not be used to characterise polluted and non-polluted sites, as there were no dominant taxa which were representative of these sites. The results presented in this thesis indicate that R. propinqua has strong potential to be a good candidate species as a bioindicator of environmental contamination. Furthermore, the full life-cycle toxicity test could be used as a rapid test to detect immediate changes in individual reproduction and development as well as long-term population effects. The technologies developed as part of this research may eventually provide additional tools for commercial environmental consultancies and may compliment existing standard operating procedures for environmental assessments involving pollution of estuarine ecosystems.
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Lapeika, Mantas. "Cinko sulfido plonų sluoksnių tyrimas skenuojančio zondo mikroskopijos (SZM) metodu." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2012. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2012~D_20120802_133914-84677.
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Darbe analizuojami ZnS ploni sluoksniai, gauti vakuuminio garinimo būdu. Tyrimai atliekami skenuojančio zondo mikroskopijos metodu. Ištirta plonų sluoksnių paviršiaus struktūra ir įvertintas gamybos metodo kokybiškumas. Išmatavus srovių priklausomybes nuo įtampų, esant skirtingoms bandinio temperatūroms, sudarytos voltamperines charakteristikos (VACh), tokiu būdu nustatytas ZnS plėvelės laidumo mechanizmas. Įvertinta aktyvacijos energija (lygi 0,64 eV). Nustatyta, kad srovę tiriamoje struktūroje sąlygoja elektronų tuneliniai šuoliai iš paviršinių puslaidininkio būsenų dalyvaujant fononams. Remiantis gautais duomenimis galima teigti, kad vakuuminio garinimo metodu gauti ZnS sluoksniai pasižymi dideliais paviršiaus netolygumais.The paper analyzes the ZnS thin films obtained by vacuum evaporation. Research carried out by scanning probe microscopy. The structure of thin layers surface is investigated and the quality of the production method is assessed. Measuring the voltage dependence of currents at different sample temperatures concluded voltage characteristics (VACh), thus the conduction mechanism of ZnS films was determined. Estimated thermal activation energy is 0.64 eV. It was found that the electrical current of the investigated structure is determined by tunneled electron jumps from the semiconductor surface states in the presence of phonons. Experiments results show that the ZnS layers produced by vacuum evaporation method are characterized by large surface irregularities.
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Winter, Lawrence Stephen. "The genesis of ‘giant’ copper-zinc-gold-silver volcanogenic massive sulphide deposits at Tambogrande, Perú : age, tectonic setting, paleomorphology, lithogeochemistry, and radiogenic isotopes." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/773.
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The ‘giant’ Tambogrande volcanogenic massive sulphide (VMS) deposits within the Cretaceous Lancones basin of northwestern Perú are some of the largest Cu-Zn-Au-Ag-bearing massive sulphide deposits known. Limited research has been done on these deposits, hence the ore forming setting in which they developed and the key criteria that permitted such anomalous accumulation of base-metal sulphides are not understood.
Based on field relationships in the host volcanic rocks and U-Pb geochronology, the deposits formed during the early stages of arc development in the latest Early Cretaceous and were related to an extensional and arc-rift phase (~105-100 Ma, phase 1). During this time, bimodal, primitive basalt-dominant volcanic rocks were erupted in a relatively deep marginal basin. Phase 1 rhyolite is tholeiitic, M-type, and considered to have formed from relatively high temperature, small batch magmas. The high heat flow and extensional setting extant during the initial stages of arc development were essential components for forming a VMS hydrothermal system. The subsequent phase 2 (~99-91 Ma) volcanic sequence comprises more evolved mafic rocks and similar, but more depleted, felsic rocks erupted in a relatively shallow marine setting. Phase 2 is interpreted to represent late-stage arc volcanism during a waning extensional regime and marked the transition to contractional tectonism.
The Tambogrande deposits are particularly unusual amongst the ‘giant’ class of VMS deposits in that deposition largely occurred as seafloor mound-type and not by replacement of existing strata. Paleomorphology of the local depositional setting was defined by seafloor depressions controlled by syn-volcanic faults and rhyolitic volcanism. The depressions were the main controls on distribution and geometry of the deposits and, due to inherently confined hydrothermal venting, enhanced the efficiency of sulphide deposition.
Geochemical and radiogenic isotope data indicate that the rhyolites in the VMS deposits were high temperature partial melts of the juvenile arc crust that had inherited the isotopic signatures of continental crust. Moreover, Pb isotope data suggest the metal budget was sourced almost wholly from mafic volcanic strata. Therefore, unlike the implications of many conventional models, the felsic volcanic rocks at Tambogrande are interpreted to have only played a passive role in VMS formation.
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Malaquias, João Corujo Branco. "Cu2ZnSnS4 thin films for PV: comparison of two growth methods." Master's thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/3498.
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Mestrado em Engenharia FísicaThis work focuses on a comparison between Cu2ZnSnS4 thin films with precursors grown exclusively by evaporation or by evaporation and RF Magnetron Sputtering. On the films which were grown using the second method was either sputtered ZnS or elemental Zinc. The morphology and composition of the samples was studied by SEM/EDS and their structure by XRD. Both methods were successful in producing thin films containing Cu2ZnSnS4. The samples which had their precursors grown exclusively through evaporation exhibited the most compact morphology but also were the ones that had more undesirable crystalline phases. Regarding the remaining samples, in the case where elemental Zinc was sputtered no diffusion issues were observed, whereas the ones with ZnS presented a layer of this material on the surface. This report is divided into six chapters which contain the introduction, information relative to semiconductors, Cu2ZnSnS4 solar cells, the growth and characterization techniques, the experimental procedure, results and their analysis and ends with the conclusion.
Com o presente trabalho pretende-se efectuar uma comparação entre filmes finos de Cu2ZnSnS4 cujos precursores foram crescidos exclusivamente por evaporação ou por evaporação e pulverização catódica RF com magnetrão. A morfologia e composição das amostras foram estudadas por SEM/EDS e a sua estrutura por DRX. Com ambos os métodos conseguiu-se crescer filmes finos de Cu2ZnSnS4. As amostras cujos precursores foram crescidos exclusivamente através de evaporação apresentavam uma morfologia mais compacta, contudo eram as que apresentavam maior número de fases cristalinas indesejadas. Relativamente às restantes amostras, no caso em que Zinco foi depositado por pulverização catódica, não foram observados problemas de difusão, contudo o mesmo não se verificou para as que continham ZnS, sendo que estas apresentavam uma camada deste material na superfície dos filmes. Este documento encontra-se dividido em seis capítulos que incluem a introdução, informação relativa a semicondutores, células solares de Cu2ZnSnS4, as técnicas de crescimento e caracterização, o procedimento experimental, os resultados e a sua análise e termina com a conclusão.
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Sousa, Marco António Neves de. "Estudo de Cu2ZnSnS4 obtido através de precursores metálicos e binários." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/11002.
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Mestrado em Engenharia Físicapresente dissertação tem como objetivo o estudo, de filmes finos de (CZTS) a partir de precursores elementares e binários. O trabalho aqui apresentado encontra-se dividido em duas partes. Na primeira parte foram crescidos nas mesmas condições dois filmes de CZTS com precursores elementares (cobre, , zinco, e estanho, ) e sulfurizados num forno tubular. Posteriormente foram analisados, morfológica e estruturalmente, tendo-se verificado a existência de CZTS e de fases secundarias. Concluiu-se que os filmes são idênticos pelo que o processo de produção é reprodutível. Na segunda parte foram crescidos dois filmes de CZTS com precursores binários (sulfureto de cobre, , sulfureto de estanho e zinco elementar) e sulfurizados num forno tubular, onde no primeiro filme apenas se fez uma análise de concentrações de composição e no segundo foi feito um ajuste das condições de deposição com base na primeira. Nesta parte apenas se fez a análise estrutural do segundo filme revelando a presença de CZTS e de fases secundárias de CTS. Este último foi dividido em 3 partes que foram sujeitas a tratamentos químicos diferentes: um com cianeto de potássio (KCN), um com ácido clorídrico (HCl) e outro com ambos os tratamentos. Seguidamente com estes foram preparadas células fotovoltaicas. A caracterização elétrica mostrou que apenas a célula feita com base no CZTS sujeito ao tratamento com HCl apresentou uma eficiência significativa de 0,4%. Por fim foi crescido um novo filme através de precursores binários e sulfurizado por processamento térmico rápido (RTP). Este último foi dividido em duas partes em que uma das partes foi sujeita a um tratamento de HCl. De seguida foram preparadas duas células fotovoltaicas. A caracterização elétrica mostrou que apenas a célula com o tratamento de HCl apresentou uma eficiência de 2,5%. Esta dissertação está dividida em oito capítulos: Introdução, Princípios básicos de uma célula solar, , Técnicas de crescimento e caracterização do CZTS, Crescimento dos filmes finos de CZTS, Caracterização e discussão dos resultados, Conclusões e Bibliografia.
The present dissertation, aims for the study of (CZTS) thin films from elemental and binary precursors. The work here presented is divided into two parts. In the first part, were grown, under the same conditions, two CZTS films with elemental precursors (copper, , zinc and tin, ) and sulfurized in a tubular furnace. Subsequently analysed, morphologic and structurally, having verified the existence of CZTS and secondary phases. It was concluded that the films are identical so that the production process is reproducible. In the second part, were grown two CZTS films of binary precursors (copper sulphide, and tin sulphide, and elemental zinc), and sulfurized in a tubular furnace, where in the first film only had a compositional analysis of concentrations and in the second one an adjustment was made based on the first deposition. In this part only structural analysis for second film was made revealing the presence of CZTS and secondary phases of CTS. The latter was divided into 3 parts which have been subjected to different chemical treatments: one with potassium cyanide (KCN), hydrochloric acid (HCl) and another with both treatments. Next with these, photovoltaic cells were prepared. The electric characterization showed that only the cell made based on CZTS subjected to treatment with HCl showed a significant efficiency of 0,4%. Finally a new film was grown by binary precursors and sulphurised by rapid thermal processing (RTP). Next two photovoltaic cells were prepared. The electric characterization showed that only the cell with the HCl treatment showed an efficiency of 2,5%. This dissertation is divided into eight chapters: Introduction, Basic principles of a solar cell, , Growth techniques and Characterization of CZTS, Growth of CZTS thin films, Characterization and discussion of results, Conclusions and Bibliography
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Xavier, Paulo Adriano. "Estudos espectroscópicos e de dopagem de nanocristais semicondutores de ZnS com íons Co2+ Cu2+." Pós-Graduação em Química, 2013. https://ri.ufs.br/handle/riufs/6110.
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This work reports the study of semiconductor nanocrystals, also known as quantum dots, focusing specifically on zinc sulfide (ZnS). Two different capping agents were used (glutathione and N-acetyl-L-cysteine) for the preparation of ZnS nanocrystals via aqueous route. The study aimed specifically at evaluating the efficacy of the capping agents in the stabilization of semiconductor nanocrystal suspensions towards coalescence as well as in controlling nanocrystal size and optical properties. In addition the effect of doping the ZnS nanocrystals with transition metal ions (Cu2+ and Co2+) on the photoluminescence properties has also been studied. Finally the possibility of energy transfer between the semiconductor nanocrystals and the safranine dye was also evaluated.
Spherical-shaped glutathione and N-acetyl-L-cysteine-capped ZnS nanocrystal were obtained with diameters below 5 nm free from coalescence, showing that both
iv
capping agents were efficient as stabilizers. Both capping agents lead to the formation of ZnS nancrystals with blue fluorescence, typical of the involvement of surface defect states of ZnS. However, samples prepared with glutathione exhibited higher fluorescence intensities than those obtained with N-acetyl-L-cysteine.
Upon doping glutathione-capped ZnS nanocrystals with both copper and cobalt the fluorescence intensities decreased gradually following the increase in nominal concentration of dopants, suggesting that cobalt ions played a similar role as copper. Considering both the effect on the intensities and the absence of d-d metal transitions this study suggests that doping reduced the concentration of cation vacancies as well as the involvement of at least one cobalt state in the transition processes. Changes in emission wavelength with different dopant concentrations were not observed probably owing to lack of influence on the nanocrystal size.
Finally the preliminary study of fluorescence quenching of semiconductor nanocrystals by safranine dye indicated that significantly low concentrations were able to quench the emissions. Different components of the emission band were distinctly affected. Data analysis by Stern-Volmer plots suggested the occurrence of more than one transfer processes (energy and/or electron transfer). This study will be refined in future works.No presente trabalho foram estudados nanocristais semicondutores, tambem conhecidos como pontos quanticos ou quantum dots, selecionando-se especificamente o sulfeto de zinco (ZnS). Foram utilizados ois diferentes agentes estabilizantes (glutationa e N-acetil-L-cisteina) na obtencao de nanocristais de ZnS por via aquosa. Buscou-se avaliar, especificamente, a eficiencia dos agentes tiois na estabilizacao das suspensoes de nanocristais frente a agregacao, no controle e distribuicao de tamanhos das particulas, bem como nas propriedades opticas. Estudou-se, alem disto, o efeito da dopagem com ions de metais de transicao (Cu2+ e Co2+) nas propriedades de fluorescencia. Por fim, foi avaliada a possibilidade de transferencia de energia entre os nanocristais semicondutores dopados e o corante safranina. Os nanocristais semicondutores de ZnS estabilizados por glutationa e por N-acetil-L-cisteina foram obtidos com tamanhos abaixo de 5 nm, formas aproximadamente esfericas e livres de agregacao, evidenciando que ambos agentes ii estabilizantes foram eficientes. Ambos agentes estabilizantes levaram a formacao de nanocristais com emissoes na regiao do azul, caracteristicas do envolvimento de estados de defeito de superficie do ZnS. No entanto, as amostras preparadas com glutationa apresentaram maiores intensidades de fluorescencia, quando comparadas com aquelas preparadas com N-acetil-L-cisteina. A dopagem dos nanocristais semicondutores ZnS/Glu com ions cobre e cobalto teve um efeito de diminuir as intensidades de fluorescencia dependente da concentracao nominal dos dopantes em ambos os casos, sugerindo que o cobalto atua de modo analogo ao cobre. Considerando-se tanto o efeito sobre as intensidades de emissao do ZnS quanto a ausencia de transicoes d-d do metal, o estudo sugeriu que a dopagem reduz a concentracao de vacancias de cations, bem como o envolvimento de pelo menos um dos estados eletronicos do cobalto nos processos de transicao. Nao se observou variacoes nos comprimentos de onda para diferentes concentracoes dos dopantes, provavelmente pela ausencia de interferencia no tamanho dos nanocristais semicondutores formados. Por fim, o estudo preliminar da supressao de fluorescencia dos nanocristais semicondutores pelo efeito de diferentes concentracoes do corante safranina mostrou que concentracoes significativamente baixas do corante foram suficientes para diminuir a intensidade de fluorescencia. Diferentes componentes das bandas de emissao dos nanocristais semicondutores foram influenciados de modo distinto. A analise dos dados pelos graficos de Stern-Volmer sugeriu a ocorrencia de mais de um processo de transferencia (energia e/ou eletrons). Este estudo sera aprofundado nos trabalhos futuros.
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Rhodes, Rhys William. "Controlling the morphology of nanoparticle-polymer composite films for potential use in solar cells." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/controlling-the-morphology-of-nanoparticlepolymer-composite-films-for-potential-use-in-solar-cells(6bc2a3cc-7c11-4615-a202-bead6360af99).html.
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This thesis presents an investigation into the factors affecting the morphology of hybrid inorganic/organic photoactive layers used in photovoltaic cells. Although optimisation of the organic (polymer) phase has received substantial attention, research into the morphology of the inorganic phase (semiconducting nanocrystals) remains limited. It is believed that there is a strong link between the morphology of the final photoactive film and the quality of the initial nanocrystal dispersion. To this end, two nanocrystal systems were investigated; zinc oxide (ZnO) and lead sulphide (PbS). ZnO nanocrystals were synthesised and found to possess reproducible characteristics. It was determined that colloid stability was initially dependent upon the presence of acetate groups bound to the surface, which in turn required a small quantity of methanol to be present in the organic dispersant. It was also discovered that while methanol evaporated readily from the surface of the nanocrystals, another molecule, 1-propylamine (1-PA), did not. Further investigations showed that while methanol only weakly physisorbed to the surface of ZnO nanocrystals, 1-PA formed strong, dative covalent bonds with Zn2+, preventing evaporation despite a low boiling point. Subsequent investigations into the effects of different ligands upon colloid stability found that amine-based groups typically possessed superior stabilising capabilities compared to alcohol-based analogues. The characteristics of nanocrystal / polymer blends were also investigated. It was determined that the nanocrystal dispersion became unstable at higher concentrations of polymer due to depletion aggregation. Films of nanocrystal / polymer blends were cast from dispersions containing either alcohol or amine-based ligands, and it was observed that dispersions stabilised with 1-PA possessed smooth morphologies on the micrometer scale. Investigations at the nanometer scale, however, revealed aggregates large enough to favour recombination.The latter half of this thesis regards the characterisation of PbS nanocrystals and investigations into triggered aggregation. It was determined that while PbS nanocrystals possessed reproducible characteristics, the stabilising molecule, oleic acid (OA) was insulating. The effects of exchanging the OA groups for a shorter ligand, butylamine (BA) were investigated.Finally, PbS nanocrystals were treated with a bidentate ligand, 1,2-ethanedithiol (EDT) to induce triggered aggregation. It was observed that the system was highly sensitive to the concentration of EDT in dispersion, forming small, relatively dispersed aggregates at low [EDT], and micrometer-sized crystalline structures at high [EDT]. The characterisation and entrapment of these nanocrystal structures within semi-conducting polymer films is also discussed.
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Stalder, Marcel. "Petrology and mineral chemistry of sulphide ores and associated metalliferous rocks of the Gamsberg Zn-Pb deposit, South Africa : implications for ore genesis and mineral exploration." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16072.
Full textAbstract:
Thesis (PhD)--University of Stellenbosch, 2004.ENGLISH ABSTRACT: The Gamsberg Zn-Pb deposit is a metamorphosed and multiply deformed sediment-hosted base metal deposit in the central Namaqua Province of South Africa. The deposit is hosted by the Bushmanland Group, a late Palaeoproterozoic (2000-1600 Ma) supracrustal succession of quartzite, metapelitic schist and interbedded metavolcanic rocks. Mineralisation occurs within the central part of the Gams Formation, a heterogeneous sequence of metamorphosed metalliferous sediments and fine-grained organic-rich shales. The ore horizon is subdivided into a lower unit of metapelite-hosted ore, an intermediate layer of phosphorite-hosted ore, and an upper unit of banded garnet-apatite ore. The ore body is enveloped by unmineralised silicate-, carbonate- and oxide-facies metalliferous rocks, which originally represented mixtures of Fe-Mn-rich hydrothermal precipitates, authigenic carbonate, and variable concentrations of detrital material. Based on mineralogical and geochemical characteristics, the metalliferous host rocks are subdivided into iron formations, coticules, Fe-Mn silicates, impure marbles and barite/Ba-rich quartzite. Minerals of the Gams Formation mostly represent solid solution between the Fe and Mn end-members of garnet, pyroxene, pyroxenoid, amphibole, olivine, spinel and ilmenite. Calcium-rich rock types are a typical feature and characterized by the occurrence of manganoan calcite, clinopyroxene, andradite-rich garnet and titanite. A successive increase in the (Mn+Ca):Fe value of rocks and minerals is evident with increasing distance from the ore horizon. Amphibole is restricted to Fe-rich ore-bearing assemblages, whereas orthopyroxene, clinopyroxene, Fe-rich pyroxenoid and olivine are present in intermediate assemblages, and Mn-rich rhodonite and pyroxmangite in the most manganiferous assemblages. These variations are mimicked by an increase in the Mn:Fe value of coexisting garnet and ilmenite group minerals with increasing distance from ore. LA-ICP-MS analyses have been used to constrain the REE patterns of garnet and apatite. In the ore-body, these minerals display a positive Eu anomaly, which is interpreted to reflect a distinct hydrothermal signature. In contrast, garnet and apatite in unmineralised metalliferous rocks display nil or a negative Eu anomaly. Primary features of the Gams Formation, such as REE patterns, the banded nature of garnet-apatite ore, the presence of diagenetic apatite nodules, and the distribution of the redox-sensitive elements Ba and Mn have been used to constrain palaeo-environmental conditions. The results indicate that metapelitehosted ore has been deposited in a stratified ocean that was characterised by anoxic bottom waters and precipitation of Fe and Zn sulphides into organic matter-rich shales. These rocks were superceded by phosphorite-hosted ore, garnet-apatite ore and metalliferous host rocks that developed in a suboxic to oxic environment. The large size of the deposit, the internal lamination of the ores and the predominance of sphalerite and barite are consistent with a vent-distal setting and precipitation of the ore-forming constituents from dense and reduced hydrothermal fluids, which originated due to reactivation of dormant growth faults. Collectively, the geological evidence indicates that Gamsberg is bridging the gap betweenthe SEDEX and BHT classifications. The relationships demonstrate that differences between these two classes of sediment-hosted Zn-Pb deposits are predominantly related to environmental conditions within localised third order basins and not to fundamental differences in ore-forming processes.
AFRIKAANSE OPSOMMING: Die Gamsberg Zn-Pb afsetting is ‘n meerfasig vervormde en gemetamorfiseerde sedimentgesetelde onedel metaal afsetting in die sentrale Namakwa Provinsie van Suid Afrika. Die afsetting word geherberg deur die Boesmanland Groep, ‘n laat Paleoproterosoïse (2000 – 1600 Ma) bokors-opeenvolging van kwartsiet, metapelitiese skis en tussengelaagde metavulkaniese gesteente. Mineralisasie word gevind in the sentrale deel van die Gams Formasie. Die Gams Formasie is ‘n heterogene opeenvolging van gemetamorfiseerde metaalhoudende sediment en fynkorrelrige organiese skalie. Die erts horison word onderverdeel in ‘n onderste laag van metapeliet-gesetelde erts, n sentrale laag van fosforiet-gesetelde erts, en ‘n boonste laag van gebande granaat-apatiet erts. Die erts-liggaam word omhuls deur ongemineraliseerde silikaat-, karbonaat- en oksied-fasies metal-ryke rotse. Hierdie gesteentes word geinterpreteer as oorspronklike mengsels van Fe-Mn-ryke hidrotermale partikels, outigeniese karbonaat, en verskeie hoeveelhede detritale materiaal. Gebaseer op mineralogiese en geochemiese kenmerke word hierdie rotse onderverdeel in ysterformasies, „coticules“, Fe-Mn silikate, onsuiwer marmer en barite/Ba-ryke kwartsiet. Minerale van die Gams Formasie form meestal soliede oplossingsreekse tussen die Fe en Mn endlede van granaat, pirokseen, piroksenoid, amfibool, olivien, spinel en ilmeniet. Kalsium-ryke rots tipes is ‘n tipiese kenmerk van die Gams Formasie en word gekenmerk deur mangaan-ryke kalsiet, klinopirokseen, andradiet-ryke granaat en sfeen. Daar word ‘n stapsgewyse vergroting van die (Mn+Ca):Fe verhouding in gesteentes en minerale gevind met toeneemende afstand van die erts horison. Amfibool is beperk tot Fe-ryke ertsdraende gesteentes, ortopirokseen, klinopirokseen, Fe-ryke piroksenoid en olivien tot intermediêre gesteentes, en Mn-ryke rodoniet en piroksmangiet tot Mn-ryke gesteentes. Hierdie variasies gaan gepaard met vergroting van die Mn:Fe verhouding in granaat en ilmeniet-groep minerale met toeneemende afstand van die erts. LA-ICP-MS analises was gebruik om die skaars-aarde element patrone van granaat en apatiet te bepaal. In die erts-liggaam wys hierdie minerale ‘n positiewe Eu anomalie, wat geinterpreteerd word as ‘n hidrotermale kenmerk. In ongemineraliseerde gasheer gesteentes wys granaat en apatiet geen of ‘n negatiewe Eu anomalie. Primêre kenmerke van die Gams Formasie, soos skaars-aarde patrone, the gebande voorkoms van granaat-apatiet erts, die teenwoordigheid van diagenetiese apatiet knolle, en die verspreiding van die redox-sensitiewe elemente Ba en Mn, was gebruik om afleidings oor die paleo-omgewing te maak. Die resultate het gewys dat metapeliet-gesetelde erts afgeset was onder anoksiese bodem water deur presipitasie van Fe en Zn sulfiedes in organiese skalie. Hierdie erts gaan oor in fosforiet-gesetelde erts, granaat-apatiet erts en metaal-ryke gasheer gesteente wat in ‘n suboksiese tot oksiese omgewing ontstaan het. Die grootte van die afsetting, die interne gelaagdheid van die erts, asook die teenwoordigheid van sfaleriet en bariet dui op ‘n distale omgewing relatief tot die hidrotermale bron en presipitasie van die ertsuit digte en gereduseerde hidrotermale vloeistowwe, wat ontstaan het deur die heraktiveering van rustende groeiverskuiwings. Gesaamentlik bewys die geologiese kenmerke van Gamsberg dat gemetamorfiseerde SEDEX en Broken Hill-tipe mineralisasie binne die perke van ‘n enkele afsetting kan voorkom. Die geologiese verhoudings dui aan dat verskille tussen hierdie twee tipes van sedimentgesetelde afsettings meestal veroorsaak word deur omgewings-toestande binne in gelokaliseerde derde orde komme en nie deur fundamentele verskille in ertsvormende prosesse nie.
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Tchoumou, Martin. "Hydrometallurgie du cuivre en milieu chlorure : attaques de minerais dosages polarographiques des solutions resultant de l'attaque et depot cathodique du cuivre." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13154.
Full textAbstract:
Etude dans le cadre de l'extraction de cu des minerais de type chalcopyrite. Lors de l'attaque des minerais de type chalcopyrite par des solutions de cu(ii) en milieu fortement chlorure, les metaux presents dans le minerai sous forme de sulfures passent en solution soit partiellement soit en totalite, et s elementaire precipite. Mise au point du dosage polarographique des ions cu, pb, zn et fe dissous. L'electrolyse de solutions a teneur elevee en cu(i) et contenant pb(ii), zn(ii) ou fe(ii) a mis en evidence un phenomene de codeposition de pb avec cu lorsqu'on opere a des densites de courant elevees, tandis que ni zn ni fe ne se codeposent avec cu
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Holder, Jenna Ka Ling. "Quantum structures in photovoltaic devices." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:d23c2660-bdba-4a4f-9d43-9860b9aabdb8.
Full textAbstract:
A study of three novel solar cells is presented, all of which incorporate a low-dimensional quantum confined component in a bid to enhance device performance. Firstly, intermediate band solar cells (IBSCs) based on InAs quantum dots (QDs) in a GaAs p-i-n structure are studied. The aim is to isolate the InAs QDs from the GaAs conduction band by surrounding them with wider band gap aluminium arsenide. An increase in open circuit voltage (VOC) and decrease in short circuit current (Jsc) is observed, causing no overall change in power conversion efficiency. Dark current - voltage measurements show that the increase in VOC is due to reduced recombination. Electroreflectance and external quantum efficiency measurements attribute the decrease in Jsc primarily to a reduction in InGaAs states between the InAs QD and GaAs which act as an extraction pathway for charges in the control device. A colloidal quantum dot (CQD) bulk heterojunction (BHJ) solar cell composed of a blend of PbS CQDs and ZnO nanoparticles is examined next. The aim of the BHJ is to increase charge separation by increasing the heterojunction interface. Different concentration ratios of each phase are tested and show no change in Jsc, due primarily to poor overall charge transport in the blend. VOC increases for a 30 wt% ZnO blend, and this is attributed largely to a reduction in shunt resistance in the BHJ devices. Finally, graphene is compared to indium tin oxide (ITO) as an alternative transparent electrode in squaraine/ C70 solar cells. Due to graphene’s high transparency, graphene devices have enhanced Jsc, however, its poor sheet resistance increases the series resistance through the device, leading to a poorer fill factor. VOC is raised by using MoO3 as a hole blocking layer. Absorption in the squaraine layer is found to be more conducive to current extraction than in the C70 layer. This is due to better matching of exciton diffusion length and layer thickness in the squaraine and to the minority carrier blocking layer adjacent to the squaraine being more effective than the one adjacent to the C70.
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Lew, Richard W. "The removal of cobalt from zinc sulphate electrolytes using the copper-antimoney process." Thesis, 1994. http://hdl.handle.net/2429/4961.
Full textAbstract:
At Cominco's zinc refinery located at Trail, British Columbia, impurities are removed from zinc
sulphate electrolyte by a two stage purification process using zinc dust. Copper, cadmium and
thallium are removed in the first stage whereas cobalt is removed in the second stage. Cobalt
removal kinetics are affected by soluble antimony and copper additions to the electrolyte. This
study was focused on the kinetics of cobalt removal by zinc powder cementation. Experimental
variables included copper and antimony concentrations, pH and temperature. Common organic
additives employed in zinc plants were studied to determine potential interactions with the cobalt
removal process. Cementation products obtained from laboratory experiments and plant practice
were studied using the SEM. A number of significant findings were observed.
1) Cobalt removal was extremely slow in the absence of any activators in solution. Batch testing
have shown that antimony activation performed better than copper activation, but the addition of
both copper and antimony together increased the rate of cobalt removal significantly. Copper and
antimony ions were essentially removed from solution during the early stages of the cementation
reaction (within the first 15 minutes), presumably, establishing the cathode surface for cobalt
removal.
2) The cobalt removal rate constant increased with increasing temperature, and the highest rate
was obtained at 90°C (the highest temperature tested). An apparent energy of activation of 86.6
kJ/mol was calculated for this system, and this value was consistent with activation controlled
processes.
3) pH significantly affected the cobalt cementation rate constant. Too low a pH (<4.0) increases
the rate of the competing hydrogen reduction reaction and too high a pH (>4.0) can result in
passivation of the residue's surface. In both these extreme ranges, cobalt removal was
detrimentally affected.
4) A drop in the cobalt removal rates can be correlated with a rise in the E^ of the slurry. Lignin
sulphonate, Percol 351 and animal glue at levels of 2 mg/L significantly impede cobalt
cementation.
5) SEM analyses of the cementation residues have shown that the activation agents and the
cobalt impurity was collected onto an impurity shell surrounding the dissolving zinc particle. This
shell consisted mainly of Zn and minor constituents of Co, Cu and Sb.
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Tzu-YingTsao and 曹姿盈. "The filitability improvement of anglesite–sludge produced by sulphate acid leaching of crude zinc oxide." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/62291041446196670101.
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Chiyangwa, Ellen. "The evaluation of polarization parameters as quality predictors for zinc electroplated from acidic sulphate solutions." Diss., 2015. http://hdl.handle.net/2263/50855.
Full textAbstract:
Successful commercial electrowinning and refining of metals typically requires the optimization of the electrolyte composition and operating parameters to produce high quality compact electroplated metal. The prediction of the structure and morphology of the plated metal from the operating parameters remains a challenge. The aim of this work was to develop a reliable galvanodynamic technique to measure nucleation and plating potentials that was specifically applicable to the plating of zinc from sulphate electrolytes, with which plant operation may be controlled and optimized. The work was focussed on determining whether there would exist a definite unique or range of values for both the nucleation and plating potentials for which it would be possible to obtain high quality zinc electrodeposits repeatably. Such a tool could be modelled and be particularly useful in plant situations to suggest remedies for process upsets and development.
In the current study a repeatable and reliable galvanodynamic polarization technique using two scan rates was developed to perform the polarization measurements. The values were used to predict the nature and morphological characteristics of the metal plated from the respective acidic aqueous zinc sulphate electrolytes
The developed galvanodynamic technique was found to be an effective and reliable technique to measure nucleation and plating potentials systematically and repeatably. The results indicated that nucleation and plating potentials could be obtained with reasonable repeatability of ±3mV. These potentials provided useful data and information on the electrowinning processes and the effect of changes in parameters and conditions of zinc deposition on the morphology. The repeatability and relevance of the potential measurements were strongly dependent on strict adherence to consistency in electrode preparation procedures, electrolyte preparation and control of experimental conditions. .
The relationship between initial nucleation of zinc on an inert aluminium substrate and further growth provided a useful framework for relating the physical changes in the structure of electrodeposits. The difference between the nucleation and plating potentials was observed to be an indicator of the type, quality and characteristics of the deposits formed, and could be used to identify a unique region which is considered to be the region in which the most desirable quality deposit will be obtained. However the idea suggested by Adcock et al. (2002), that nucleation is favoured over growth if the plating potential is more negative than the nucleation potential ΔE, and should therefore result in unoriented dispersion (UD) type deposits turned out to be only partly so with such deposits rather obtained for ΔE values around zero and with field oriented texture (FT) and basis reproduction (BR) type deposits obtained at more positive as well as negative values.
The effect of temperature on the plating characteristics was not significant. This may have been attributed to the influence of hydrogen ion reduction on the potential whereby a substantial current flow and a shift of potentials to positive values is observed, but not necessarily due to zinc plating. Higher temperatures showed a considerable reduction in current efficiency which is a consequence of high rates of hydrogen reduction. This indicated that the approach to characterise zinc plating by polarization characteristics would probably not be valid for conditions where significant rates of hydrogen ion reduction occur.
The study indicated that grain refiners influence the nucleation process while levellers change the growth process. The difference between the plating and nucleation potentials ΔE was found to be an indicator for identifying and predicting grain refinement but not as much as in the case with levelling. This limits the usefulness of the two dimensional representation of the polarization parameters, such as suggested by Adcock, for the evaluation of additives for zinc electrowinning from sulphate electrolytes.Dissertation (MSc)--University of Pretoria, 2015.
tm2015
Materials Science and Metallurgical Engineering
MSc
Unrestricted
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Wang, Chunzheng. "Electron paramagnetic resonance and optical-absorption studies on Cu²⁽ r impurity in single/poly crystals of hydrated monopyrazine zinc sulphate, (cadmium, nickel, magnesium)-ammonium sulphate, and magnesium acetate." Thesis, 1990. http://spectrum.library.concordia.ca/5901/1/NN64677.pdf.
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Lehmann, Matthew Karl Wilhelm. "Biooxidation of a zinc sulphide ore." Thesis, 2003. http://hdl.handle.net/2429/14435.
Full textAbstract:
An experimental program was conducted on a zinc-sulphide ore containing 15% zinc in
support of the development of the Teck Cominco HydroZinc™ process. The two primary
types of experiments that were conducted were bacterially assisted short column experiments,
and controlled potential, isothermal, chemical leaching experiments.
This program was carried out in order to determine the kinetics of heap biooxidation of this
zinc ore at controlled temperatures, and to determine the rates of heat generation under those
conditions. In addition, the ores' topology, activation energy, and dependence on ferric and
ferrous ions were determined.
Once the primary objective of generating consistent, meaningful data was achieved, a
concerted effort was made to fit the results with an existing mathematical model. This
exercise was met with mixed results and it was concluded that the mathematical model, in its
current stage of development, is insufficient to accurately describe the leaching of this ore.
It was concluded from both the experimental data and the mathematical fits that the rate of
bacterial leaching of this zinc ore is limited by transport of oxygen into solution. Results of
the potentiostatic experiments indicate that the ore follows a variable order model, has an
activation energy of 58.23 kJ mol ⁻¹, a reaction order of 2.30, and a dependency on ferric ions
of O.342.