To see the other types of publications on this topic, follow the link: Lead – Metallurgy.
Dissertations / Theses on the topic 'Lead – Metallurgy'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Lead – Metallurgy.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Vineberg, Daryl Geoffrey. "A study of lead softening /." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80149.
Full textAbstract:
Softening represents one of the stages in the pyrometallurgical refining of lead, in which oxygen is top-blown into a bath of impure bullion through a group of lances in order to preferentially oxidize arsenic, antimony and tin dissolved in the melt. The oxides of these species float to the melt surface, where they are removed as dross.It has been observed at Teck Cominco Lead Operations in Trail, BC that there is an "ignition temperature" in the range of 600°C, below which the softening reactions are reported to occur very slowly, if at all. Currently, disproportionately large efforts are made to initiate and sustain the softening process. This research was motivated by Teck Cominco's wish to have a clearer understanding of the ignition temperature phenomena, and a more robust and reliable process control.
Experimental trials were performed using a homemade thermogravimetric analyzer with a data acquisition system. The unit was constructed in such a way as to allow for simultaneous video recording of the sample surface, for future examination and reference.
2
Firoozi, Sadegh. "Thermodynamics and mechanisms of lead softening." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100362.
Full textAbstract:
Visualization and quantitative oxidation kinetic experiments on 100 g samples of Pb-As at 600°C; thermal analysis and phase-equilibrium measurements of Pb-PbO-As2O3 samples under argon over the temperature range of 420°C to 875°C; computational thermodynamic solution modeling; and phase diagram and equilibrium calculations using FACTSage(TM) were performed to elaborate the poorly documented thermodynamics of the slags in the lead softening stage in the pyrometallurgical refining of lead. In the softening stage, the minor element impurities: arsenic, antimony and tin are removed from lead bullion by oxidation and are transferred to a skimmable oxide slag phase.It was found that optimizing an ionic molten oxide solution model that was conceptualized to contain Pb2+ and O2- with AsO3-4 and AsO3-3 ions, or with SbO3-4 and SbO3-3 ions in the respective PbO rich regions of the Pb-As-O and the Pb-Sb-O systems, was able to accurately reproduce the measured and published thermodynamic data. It was also found that the subsystems in the PbO-As2O 3-As2O5 and PbO-Sb2O3-Sb 2O5 systems showed small deviation from the ideal ionic solution model and small magnitude excess Gibbs energy parameters were sufficient to fit the predicted liquidus curves to the experimental measurements.
Arsenic in the +3 and +5 oxidation states was measured in the PbO rich region of the Pb-As-O liquid solution in the temperature range of 420°C to 875°C. The variability in the ratio of trivalent arsenic to the total arsenic content, as well as the complex variation of arsenic distribution between metal and oxide phases found strong interaction between the lead, arsenic and oxygen atoms at the 3PbO to 1AS2O3 molar ratio thus suggesting a short range ordering corresponding to the formation of AsO3-3 groupings, and indicating that the Pb3(AsO3) 2(l) species was likely to be present in the PbO rich region of the Pb-As-O system and contributing to an understanding of the Pb-As-O liquid oxide structure. Also, two new compounds (Pb3(AsO3) 2(s), Pb2AsO4(s)) were identified in the Pb-PbO-As 2O3 quenched samples via wavelength-dispersive spectrometry using the electron microprobe. The present work has application in commercial oxygen partial lead softening (OPLS), as uniquely practiced at Teck Cominco Ltd., British Columbia. There, pure oxygen gas is injected into the bath of impure bullion through a number of submerged lances in order to oxidize only part of the arsenic, antimony and tin into a slag phase. For such an operating practice, it was concluded from the visualization and quantitative oxidation experiments that the formation of solid oxides as the product of oxidation produced a physical barrier to the progress of oxidation and resulted in the commercially observed, highly-problematic, process initiation issues. When the product was liquid, there was much less of a barrier to rapid oxygen mass transfer to the minor element impurities and the softening reactions were easy to initiate. Such a change in the physical state of the products of oxidation was correlated to the optimized ternary Pb-As-O and Pb-Sb-O phase diagrams.
A current point of interest in partial lead softening is to increase the arsenic content of the slag phase. Arsenic distribution between lead bullion and slag calculated by the optimized solution model of the Pb-As-O system suggests that this can be achieved in a counter-current contacting of the slag and bullion.
3
Weller, Sean David Tomey. "Lead-free solder technology." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/5575/.
Full textAbstract:
Aerospace applications typically require electronic products with not only higher levels of reliability than the consumer electronics industry but also longer service lives within demanding working environments. The transition will inevitably mean changes to design and manufacturing procedures, which is likely to incur a significant cost to the business. For example, the best candidate Pb-free solder alloys have been shown to require higher soldering temperatures and have higher surface tensions. Moreover, a reduction in product safety and reliability is not acceptable to the industry. This present work is divided into three sections. Firstly, the effect of increased component soldering temperatures on the integrity of the epoxy laminate material used for manufacture of printed circuit boards (PCB) has been assessed. Secondly, the required changes in soldering process parameters have been investigated for a range of solders and PCB finishes, largely due to the different wetting characteristics brought about by the increased surface tension of the Pb-free solders. Thirdly, the reliability of SnAgCu solder is assessed in comparison to the currently utilised SnPbAg solder alloy. This has been achieved firstly by accelerated thermal cycling, as the dominant mode of failure in a solder joint is typically thermo-mechanical fatigue and as such is already well researched. In addition, the mechanical fatigue properties have been assessed using a novel accelerated vibration test method and then finally, the two individual accelerated environmental tests of thermal cycling and vibration have been combined in a novel way to assess whether the combination is especially dangerous for SnAgCu solder reliability. A secondary objective of the combined environment test was to see if the well established thermal cycling test method for demonstration of product reliability can be further accelerated while still producing solder joint failure representative of those in-service. The present work shows that SnAgCu solder has inferior thermo-mechanical and mechanical fatigue life to SnPbAg solder. A combined environment test has been developed which effectively combines the single environments of thermal and vibration. The combination of thermal cycling with superimposed vibration is especially dangerous for SnAgCu solder, where an 89% reduction in the characteristic life is observed when compared to the equivalent thermal cycling characteristic life. It is suspected that a large reduction in life will be observed in SnPbAg solder, but not as pronounced as SnAgCu due to SnPbAg solders ability to better withstand plastic deformation that is induced by thermal cycling.
4
De, Santis Donato. "Hydrogen reduction of lead from Kelex 100." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66077.
Full text
5
Khan, M. M. "Selective flocculation of lead-zinc concentrate." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355440.
Full text
6
Williams, C. P. "Synthesis of lead zirconate titanate powders." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268127.
Full text
7
Stålnacke, Emil. "Microstructure-corrosion interrelations in new low-lead and lead-free brass alloys." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217355.
Full textAbstract:
In new low-lead and lead-free brass alloys, it is not understood how the corrosion properties,such as dezincification, are related to material composition as well as annealing temperatureand duration. This study aims to fill this knowledge gap by mapping sixteen annealingconditions and three different brass alloy compositions to their respective microstructure anddezincification performance. It was found that high dezincification depth was a result ofannealing temperatures at 300°C – 400°C, which promoted precipitation of intermetallicAlAs-particles along grain boundaries, twins and lead particles as well as precipitation of β-phase along grain boundaries. Their presence was correlated to high micro additions ofaluminium or iron in the material composition. An additional compositional factorcontributing to precipitation of high amount of β-phase was low copper/zinc-ratio.
8
Rohde, Michael D. "Recovery of silver from lead/zinc flotation tailings /." [St. Lucia, Qld], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18254.pdf.
Full text
9
Neiström, Linda. "Characterisation of Used Lead-Acid Batteries for Feed Optimisation in Secondary Lead Production." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70740.
Full textAbstract:
Used lead-acid batteries are the main raw material in secondary lead production. Technologicalprogress in the car industry, have raised concerns regarding the lead-acid battery’s leading positionas electrochemical storage system in the future. However, the lead-acid battery industry isadvancing with innovations, such as hybrid and micro-hybrid vehicles, and is believed to have acontinued important role in the rechargeable battery market. Lead is one of the most investigatedmetal due to concerns from society regarding the negative effect on human health and theenvironment. Consequently, that has led to tighter controls and regulations of the lead processingindustry which, in turn, has led to technological improvement concerning design and operation ofthe lead processing plants. Used lead-acid batteries have a complex composition with a variety ofcomponents made of lead (i.e., metallic, oxide or sulphate) and non-lead materials (plastics andelectrolyte). Traditionally, battery recycling is done without separating those components.However, to optimise the use of resources and decrease the environmental impact of secondarylead production, a pre-treatment step to the batteries recycling is desired. The pre-treatment iscomprised of breaking the batteries and separation of the battery components. The aim of the present thesis, was to study the components of a used lead-acid battery, which willbe the outgoing material of a future plastic separation plant at Boliden Bergsöe, and their effect onthe process. Furthermore, the study aimed at investigating the possibilities to adjust the feedcomposition for further process optimisation and improvement of the process quality in terms ofenergy usages and environmental impact. This was done by characterise, through qualitative andquantitative composition and mass distribution, the fractions in a used lead-acid car battery. Four lead-acid car batteries were provided for dismantling to study mass distribution, and toliberate the components for further analysis. The analytical techniques used in this study werequalitative and quantitative (Rietveld) XRD analysis, SEM-EDS and TGA. The result showed thatoverestimated amount of battery separators (PE) has been used at production planning in energyandemission calculations, which can cause financial losses due to overpaid emission tax. The pastefraction showed a large variation in mass between the studied batteries and consists mostly ofPbSO4. Large variation in the paste mass may cause uneven sulphur emission from smelter.Consequently, this reinforces the need for implementation of the separation of the battery feed fora better control of the paste addition to the smelter. When PE decomposes in the shaft furnace the remaining ash will mainly consist of silica, whichwill affect the sulphur uptake in the shaft furnace. The large content of silica leads to a lower energycontribution to the process; however, a lower content of hydrocarbons leads to lower CO2emissions. If a desulphurisation of the pastes would be implemented, it is believed to affect theprocess through a decreased need of coke and iron. A reduced usage of coke and iron would lowerthe production costs and lead to decreased CO2 emissions. A desulphurisation will also decreasethe lead sulphate content in the feed, thus lead to better control of the sulphur emissions. This study provides additional support and further insight into composition and mass distributionof the components in a lead-acid battery. Furthermore, the study indicates possible impact of thefuture separation on the new feed properties and on the subsequent processing.
10
Ward, Andrew. "Development of a lead-free aluminium bearing alloy using powder metallurgy manufacturing techniques." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/6418/.
Full textAbstract:
This study, completed with the University of Birmingham, was sponsored by Controls and Data Services (CDS) and the Engineering and Physical Sciences Research Council (EPSRC). A range of materials and processes were evaluated with the aim of producing a lead-free, monolithic, machinable plain bearing to replace the leaded bronze gear pump bearings currently used. The primary alloys investigated in this thesis were Al-20Sn-7Si-1Cu and an Al-20Sn-7Si- 1Cu-1Mg wt% composition; with the latter achieved by the controlled addition of Al- 50Mg wt% master alloy. The project identified an aluminium-tin-silicon based alloy that could be sintered to near 100% of theoretical density in the manufacture of a ¾ scale rod form. The process and material produced should be capable of replacing the bearing alloys typically used in aerospace pump applications. The addition of magnesium, with controlled morphology and size, and the parallel use of a nitrogen sintering atmosphere, significantly improved the heat treated density of these materials. Successful sintering, typically completed at 500°C, could be significantly reduced in time by the use of pressurised nitrogen from 20 hours to 5 hours. The sintered microstructure generated was a heat treatable aluminium / copper matrix with desirable, discrete regions of silicon (typically 3 – 4 microns in size) and reticular tin.
11
Halici, Safak. "Development Of Lead Alloys For Valve-regulated Lead-acid (vrla) Batteries." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612422/index.pdf.
Full textAbstract:
In this study, Mg, Sn, Cd, Bi and Sb containing, five binary, three ternary and two quaternary different alloys to be used in a Valve-Regulated Lead-Acid (VRLA) batteries have been studied in terms of their mechanical and electrochemical properties. The investigated properties are hardness, passivity, corrosion rate, hydrogen gassing and the conductivity of the passive film. All electrochemical tests were carried out in 3.75 M H2SO4 solution by using open-circuit potential, anodic polarization, polarization resistance measurement and gas collection techniques.
The results showed that while the minimum hardness values were observed in Pb and Pb-Bi alloy, Mg containing alloys have the highest hardness values among all alloys. According to corrosion measurements, lowest icritical value was obtained for Pb, Pb-Bi and Pb-Sn, which reached to passivation region earlier than others. Passive film formation was seen for all specimens. The noble Ecorr value and minimum corrosion rates belonged to Pb and Pb-Mg. Pb-Bi and Pb-Cd have the highest gas evolution rate. Besides, there were not seen much difference in the gassing behavior of Pb-Sn and Pb-Sb alloys. Mg is found to have a superior effect on hydrogen gassing. Addition of Sn, as an alloying element, to lead increases the conductivity of the passivation layer. Mg containing alloys did not show good conductivity characteristic. As a result, Mg containing alloy seemed to have an important role because of the desired hardness, corrosion and, gas evolution behavior. However, conductivity of passivation layer of these alloys came up to be low due to the higher tendency of Mg to oxidation. Even so, Mg seems to be a promising alloying element for lead grid alloys in Valve-Regulated Lead-Acid (VRLA) batteries.
12
Thongchai, Tanikan. "Fabrication of lead free and lead based 1-3 piezoelectric composites for high frequency ultrasound transducers." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8041/.
Full textAbstract:
This thesis is concerned with the fabrication and characterisation of lead free piezocomposites and transducers for use in high frequency medical ultrasound imaging applications. A water based gel casting and micro moulding approach has been developed to fabricate 1-3 composites with a random pillar structure in the lead free and lead based piezoelectric material. High frequency transducers incorporating the random composites as the active components have been fabricated, characterised and demonstrated in real tissue imaging environments. A water based gel casting system has been used incorporating Hydantoin Epoxy resin, amine hardener (Bis (3-aminoproply) amine) and dispersant. Viscosities of the 50BCZT and PZT systems were minimised by the addition of 2.4 and 1 wt% of dispersant respectively. The highest values of piezoelectric and dielectric properties corresponded to 50BCZT samples fabricated with a gel casting slurry incorporating 30 wt% resin and sintered at 1425 °C, with d33 and kp values of 330 pC/N and 0.43, respectively. 1-3 composites were successfully fabricated from the BCZT and PZT bristle block structures and only one resonance peak corresponding to the thickness mode was observed. PZT composites offered generally higher thickness coupling coefficients than 50BCZT composites, where the highest value of 0.78 was measured for samples sintered at temperature 1425 °C. Focused PZT, focused 50BCZT, unfocussed PZT and unfocussed 50BCZT transducers were successfully fabricated using the composites with randomised structure, and have operating frequencies of 35, 40, 50 and 35 MHz respectively.
13
Hall, Bradley Devin. "Powder processing, powder characterization, and mechanical properties of LAST (lead-antimony-silver-tellurium) and LASTT (lead-antimony-silver-tellurium-tin) thermoelectric materials." Diss., Connect to online resource - MSU authorized users, 2008.
Find full textAbstract:
Thesis (M.S.)--Michigan State University. Materials Science and Engineering, 2008.Title from PDF t.p. (viewed on Aug. 7, 2009) Includes bibliographical references (p. 151-159). Also issued in print.
14
Sunkar, Ahmet Semih Supervisor :. Topkaya Yavuz A. "Investigation and development of possible leaching processes for recovery of zinc and lead from çinkur leach residues." Ankara : METU, 2005. http://etd.lib.metu.edu.tr/upload/12605886/index.pdf.
Full text
15
Farinha, Marques Vitor Manuel. "Lead free solders for aerospace applications." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:85707054-bc46-44f3-b9c6-9fd29358ad25.
Full textAbstract:
The factors controlling the reliability of Pb-free solders when subject to thermomechanical regimes relevant to the harsh aerospace environment have been studied. Ball grid array (BGAs) typical of microelectronic devices have been manufactured in-house and subjected to isothermal ageing and thermal cycling. The BGAs comprised both Cu and Ni-Au metallizations, Pb-free Sn-Ag-Cu 400 and 600μm solder balls, FR4 and Al2O3 boards, and included circuits to measure resistance changes due to damage in the joints during thermal cycling. Microstructural evolution within the solders balls and complex interfacial reactions were studied in all configurations using various types of electron microscopy. The mechanical properties of the different phases formed within solder joints were studied using nanoindentation at room and elevated temperatures up to 175°C for the first time. Intermetallic compounds (IMCs) were stiff, hard and brittle with very low creep rates, while the softer primary Sn, eutectic regions and Cu metallization readily underwent creep. Two-dimensional finite element analysis (FEA) of nanoindentation was used to understand better the physical meaning of nanoindentation creep data. Reliability experiments comprised both thermal cycling and FEA of BGAs. The difference in coefficient of thermal expansion (CTE) in the BGA materials caused interfacial fatigue damage in the solder joints, which was detected primarily at the solder/metallization interface of the outermost, most strained solder joint. Accumulated creep strain per cycle at this interface was evaluated using 3D FEA of the stress-strain state of the BGA and results calibrated against experimental BGA mean lifetimes using the Coffin-Mason relationship. Nanoindentation combined with FEA has been shown to be a viable route for the rapid assessment of creep performance and lifetime in lead-free solders under aerospace thermal cycles.
16
Tan, Lihe. "The microstructure and resistance to thermal fatigue cracking of lead-copper sheet alloys." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308321.
Full text
17
Westlake, Michael Angelo 1966. "The oxidation of copper and silver plated copper lead frames." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278279.
Full textAbstract:
The effects of thin silver films (15-210 angstroms) on the oxidation of copper alloy lead frames has been characterized. Silver films were deposited onto copper lead frames by immersion plating in a bath containing potassium silver cyanide, potassium cyanide, and a mercaptan inhibitor. The thickness of films was measured by microfocus x-ray fluorescence and cross-checked by Rutherford backscattering spectrometry. Lead frames coated with silver films were oxidized at 150 to 200°C in a controlled humidity oven. The amount of oxide formed was measured by an electrolytic reduction technique and cross-checked with weight gain measurements. Auger, ESCA, and SEM analysis were also performed on the films. A tape test was performed to obtain qualitative information on the adhesion of the films.
18
Cooper, Shellene. "Creep behaviour of the ternary lead-free solder alloy, Sn-3.8wt.%Ag-0.7wt.%Cu." Thesis, Open University, 2002. http://oro.open.ac.uk/54417/.
Full textAbstract:
Electronic equipment is facing the challenge of both miniaturisation and the need to replace lead in interconnections. In service, interconnections generally fail by thermomechanical fatigue, and this behaviour is strongly affected by the creep process. This thesis examines the creep behaviour of a popular lead-free replacement alloy, Sn-3.8wt.%Ag-0.7wt%Cu (Sn-Ag-Cu), in joint and bulk form. Experimental work involved the determination of the creep properties of this alloy at various temperatures, over a range of stresses. Over the regions tested, the creep behaviour is best described by the Norton power law constitutive equation. The stress exponent for bulk Sn-Ag-Cu ranged between 10 and 18 (at 125 to -lOoC respectively) and indicates that a dispersion-strengthened mechanism is dominant in the creep process. The activation energy for creep in the bulk Sn-Ag-Cu is approximately 120kJ/moi and falls in the region similar to that observed for the self-diffusion of tin. In joint form the stress exponent is greater than 10 at high stresses but a change in mechanism is indicated at lower stress where the creep exponent falls to 3. The activation energy for creep in Sn-Ag-Cu when used in joint form is approximately 70kJ/moi and falls in the region similar to that observed for the short-circuit diffusion of tin. Results obtained from the ternary alloy were directly compared to those from Sn- 37wt.%Pb (Sn-Pb) and other prospective lead-free alloys in bulk form. The creep resistance of the ternary lead-free alloy at 75°C is superior to the conventional Sn-Pb alloy and the possible replacement alloys (tin-copper and tin-silver). This superiority is retained when tested at similar homologous temperatures. However, the Sn-3.8Ag- O.7Cu alloy is less ductile but generally possesses strains to failure above 10 percent in comparison to the 25 to 50 percent ductility of Sn-Pb.
19
González, Domínguez José Alberto. "Electrochemical processes within the slimes layer of lead anodes during Betts electrorefining." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30919.
Full textAbstract:
In the Betts process for lead electrorefining the noble impurities originally present in the bullion form a strong and adherent layer of slimes. Within this layer the established ionic concentration gradients can lead to secondary reactions. The following processes were analyzed from a thermodynamic perspective: (A) hydrolysis of the acid (B) precipitation of secondary products (C) reaction of noble compounds.
The nature of the concentration gradients within the slimes layer and related secondary processes was studied by using transient electrochemical techniques which include: (A) current interruption, (B) AC impedance, and (C) a variation of SACV (Small Amplitude Cyclic Voltammetry). These studies were complemented by: (A) physico-chemical data on electrolyte properties, (B) "insitu" and "industrially recovered" slimes electrolyte compositions, (C) SEM and X-ray diffraction analysis of the slimes layer. For comparison purposes the electrochemical behaviour of "pure" Pb electrodes was also studied.
Upon current interruption the anodic overpotential decays, first abruptly, (as the uncompensated ohmic drop disappears) and then slowly (due to the presence of a back E.M.F. created by ionic concentration gradients that decay slowly). Current interruption measurements showed that: (A) concentration gradients exist across the slimes layer, (B) inner solution potentials within the slimes layer can be larger than those measured from reference electrodes located in the bulk electrolyte, (C) secondary products can shift the inner solution potential to negative values which reverse upon re-dissolution and (D) ionic diffusion is seen upon current interruption but it is complex and difficult to model due to the presence of processes that can support the passage of internal currents.
The anodic polarization components were obtained by analyzing the potential and current dependance upon application of a small amplitude sinusoidal waveform. This dependance was found to be linear in the low overpotential region (< 250mV). Thus, upon subtraction of the uncompensated ohmic drop, the remaining polarization is due to the "apparent" ohmic drop of the slimes electrolyte and to liquid junction and concentration overpotentials. These components are directly linked to the electrolysis conditions and to the slimes layer structure. Furthermore, the ratio of these components can be used to obtain the point at which the precipitation of secondary products starts. Changes in this ratio can also be related to the anodic effects caused by the presence of addition agents.
AC impedance measurements performed in the presence of a net Faradaic current showed that the impedance increases uniformly as the slimes layer thickens up to the point at which noble impurities start to react. Three electrical analogue models were used to describe the impedance spectra.
A steady-state mathematical model that predicts concentration and potential gradients across the slimes layer was developed. Only when a position dependent eddy diffusion term was incorporated in the numerical solution, were reasonable local ionic concentrations and overpotentials obtained.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
20
Stoneman, Alan Michael. "A determination of the factors which control the oxidation rate of agitated tin-lead alloys." Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/848061/.
Full textAbstract:
An apparent inverse dependence of oxidation rate on temperature was discovered between approximately 270°C and 295°C using 60% tin-40% lead alloy as a result of a preliminary investigation carried out to determine the effect of temperature on the oxidation and drossing rates of stirred tin-lead alloy melts. This effect was found to be dependent on time and the composition of the alloy, and coincided with a considerable rise in drossing rate. Furthermore the oxidation rate of stirred 60% tin-40% lead alloy showed a very unusual increasing rate with time. Therefore a systematic study was carried out to determine the factors which control the oxidation and drossing rates of liquid tin-lead alloys, pure tin and pure lead at temperatures between approximately 200°C and 400°C. The results of the study are reported in two parts. In the first part the effects of time, temperature, the concentration of tin in the alloy, stirring rate and the effects of additions of up to 0.2% of copper, cadmium, zinc, aluminium, antimony silver and phosphorus on the weight gain and the weight of dross formed using stirred tin-lead alloys are reported. It was found that except for a phosphorus addition of 0.01% which reduces the weight gain of stirred 60% tin-40% lead alloy by at least 50%, the additions generally show only minor effects on the weight gain dependence of the alloy on temperature. The oxidation kinetics of stirred 60% tin-40% lead alloy have been interpreted using the Arrhenius equation. Drosses were examined and analysed using scanning electron microscopy, metallography, X-ray diffraction, X-ray photoelectron spectroscopy and atonic absorption spectrophotometry. In the second part of the study the effects of temperature and air pressure on the oxidation kinetics of static melts of 60% tin-40% lead alloy, pure tin and solid lead were determined using an electromicrobalance. Generally parabolic kinetics were observed indicating that the oxidation processes involved are diffusion controlled. It was also found that the oxidation gate of static melts of 60% tin-40% lead alloy at 270°C exceeds that at 295°C using an air pressure of 250 Pa although this effect is eliminated by reducing the air pressure to 50 Pa. Furthermore the oxidation rates of liquid 60% tin-40% lead alloy, pure tin and solid lead were in general higher using the lower air pressure of 50 Pa. The results obtained in this part of the study have also been inteipreted using the Arrhenius equation. Furthermore the oxide layers were examined and analysed using scanning electron microscopy and X-ray diffraction techniques. It appears that changes in the morphology of the oxide layer on liquid 60% tin-40% lead alloy may account for the observed changes in the oxidation rate of the alloy with, temperature and air pressure. A comparison of the oxidation rates of static and stirred melts of 60% tin-40% lead alloy show clearly that the oxidation rate of the stirred alloy is controlled by the additional surface area exposed as a result of drossing. Furthermore the nature of the oxide layer appears to have a significant effect on the drossing rate of the alloy. It was also shown by calculation that the observed time dependence of the fall in weight gain of stirred 60% tin-40% lead alloy with temperature could be explained in terms of the total surface area of the alloy exposed to the atmosphere.
21
Aytekin, Kasim. "Characterization of machinability in lead-free brass alloys." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240107.
Full textAbstract:
Ny lagstiftning har lagt fokus på den tociska naturen av bly som legeringselement I mässingsprodukter. Vattenförsörjningssystem är av största oro där misstänkt blyläckage från mässingsprodukter hotar människors hälsa, världen över. Denna studie har utförts i syfte att karaktärisera bearbetbarheten av blyfria mässingslegeringar för att förse industrin med nödvändig information och underlätta att ersätta dagens blyade alternativ. Karaktäriseringen har fokuserat på två specifika bearbetningsprocesser, nämligen svarvning och borrning där intresset har legat hos skärkraftsgenerering och spånbildning. Svarvtesterna riktade sig mot att jämföra tre olika legeringar, CW511L, AquaNordicÒ och CW625N. De två förstnämnda är blyfria och CW625N är en medelblyhaltig mässingslegering. Borrtesterna riktade sig mot att karaktärisera vilken effekt borrgeometrier har på skärkraftsgenerering och spånbildning. Huvudfokus lades på inverkan av spånvinkel och borrdiameter. Borrtesterna utfördes endast på AquaNordicÒ. Resultaten har visat att, signifikant högre skärkrafter genereras vid svarvning av blyfria legeringar jämfört med blyfria. Det fanns emellertid ingen signifikant skillnad mellan de båda blyfria legeringarna avseende skärkrafter, medan spånbildning förbättrades för AquaNordicÒ . Borrtesterna har å andra sidan visat att bearbetningen hos den blyfria AquaNordicÒ -legeringen kan förbättras genom att öka på spånvinkeln och minska borrdiameter. Baserat på resultaten från det här avhandlingsarbetet har man dragit slutsatsen att bearbetningen av blyfria mässingslegeringar är tillräckligt bra för att kunna antas av industrin. Förbättring är dock nödvändig för att ersätta de blyeade alternativen helt.Recent legislation has put focus on the toxic nature of lead as an alloying element in brass products. Watersupply systems are of biggest concern where suspected lead leakages from brass products are threatening human health. A comprehensive study has been conducted in order to characterize the machinability of lead-free brass alloys to provide the industry with necessary information to assist a replacement of the leaded alternatives. The characterization has focused on two particular machining processes, namely turning and drilling and has been based on cutting force generation and chip formation. While the turning tests aimed to characterize the machinability by comparing two lead-free alloys (CW511L and AquaNordic®) with a leaded alloy (CW625N), drilling tests aimed to characterize machinability of the lead-free AquaNordic® alloy particularly, with the main focus put on the impact of tool geometry on machinability. The results have shown that significantly higher cutting forces are generated during turning of lead-free alloys as compared to the leaded. There was, however, no significant difference between the two lead-free alloys regarding cutting forces while chip formation is improved for AquaNordic®. Drilling tests have shown that the machinability of the lead-free AquaNordic® alloy can be improved by increasing the tool rake angle and decreasing tool diameter. Based on the results from this thesis work, it has been concluded that the machinability of lead-free brass alloys is sufficiently good to be able to be adopted by the industry. However, improvement is necessary inorder to fulfill the requirement needed to replace the leaded alternatives.
22
Shu, Chang. "Investigation of the structural and functional properties of lead-free barium calcium zirconate titanate piezoceramics." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8148/.
Full textAbstract:
There is an urgent desire to move from lead-based piezoelectric materials to lead-free alternatives. One of the most promising lead-free materials has been reported to be zBao.7oCao.3oTi0J-(1-z) BaZro.2oTio.soOJ (abbreviated as zBCT-(1-z)BZT) system, which has comparable piezoelectric performance to lead-based materials. However, there is a lack of systematic research to investigate the effects of fabrication on the structural and functional properties of this zBCT -(1-z)BZT system. In this work, the end member Bai-xCaxTiOJ (x=0-0.30) and BaZryTii-y03 (ji=0-0.30) systems have been investigated. The phase transition diagrams of the two systems have been successfully established by measuring temperature dependent Raman spectroscopy and functional properties. The optimized fabrication procedure for forming single phased Bao.7oCao.3oTi0J and BaZro.2oTio.soOJ ceramics by solidstate methods, has been applied as a novel way to form zBCT-(1-z)BZT (O:Sz:~:J) ceramics by sintering the pre-calcined Bao.7oCao.3oTi0J and BaZro.2oTio.soOJ powders. A new phase diagram of the zBCT-(1-z)BZT (0$z:S1) has been constructed by combing structural and functional property measurements. It indicates a vertical orthorhombic phase region separating rhombohedral and tetragonal phases below the Curie temperature. The highest piezoelectric properties have been observed for z=0.5 ceramics at room temperature, due to the increased potential polarization directions in the vicinity of the orthorhombic to tetragonal phase boundary.
23
Kantarcioglu, Anil. "Development Of New Lead-free Solders For Electronics Industry." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615186/index.pdf.
Full textAbstract:
Joining of electronic components onto the circuit boards is done by soldering operation, during production of all electronic devices. In many countries, including Turkey, traditionally used tin-lead (Sn-Pb) solder alloys have been restricted to be used in consumer electronics appliances because of the toxic effects of lead (Pb) within these alloys. Tin-silver-copper (Sn-Ag-Cu) based alloys have been developed as the most promising candidate that can replace the Sn-Pb alloys. However, various problems have emerged with the increasing trend in use of Sn-Ag-Cu solder alloys in electronics industry, namely large intermetallic compound formation, low wettability and thermal shock resistance. Many researches have been done in the past decade to overcome these problems. The solutions are based on changing the undercooling of the solder alloywhich was determined to be done by either changing the composition of the solder alloy by micro-alloying or changing the cooling rate during soldering operation. In this thesis study Sn-3.5Ag-0.9Cu (wt. %) lead-free solder having the eutectic composition, was micro-alloyed with additions of aluminum (Al), iron (Fe) and titanium (Ti). Experimental results were compared with commercially available near-eutectic Sn-40Pb (wt. %) solder, a commercially available Sn-3.0Ag-0.5Cu (wt. %) solder and also eutectic Sn-3.5Ag.0.9Cu (wt. %) and near-eutectic Sn-3.7Ag-0.9Cu (wt. %) solders that were produced for this thesis study. In the first stage of the study, the effects of 0.05 wt. % of Al, Fe and Ti micro-alloying were investigated. When preliminary results of mechanical and thermal test were compared, Fe was found to make positive effect on shear strength and undercooling. Further research was carried out to establish a relationship between the Fe compositions and solder properties. Therefore, 0.01, 0.03, 0.07 and 0.1 wt. % Fe additions were also studied and results were reported. 0.01 wt. % and 0.07 wt. % Fe added solders were found to have a smaller undercooling, resulting with dispersed intermetallic compound (IMC) and thus has highest shear strength. Different cooling rates
0.017, 0.17 and 1.7 °
C/sec were applied to solder-copper joints and microstructures were investigated. Large IMC-free microstructure was achieved by 0.01 wt. % Fe micro-alloyed solder, which was cooled with 1.7 °
C/sec rate. Wetting of copper substrate was found to be improved by additions of Al, Fe and Ti compared to alloy with eutectic composition of Sn-Ag-Cu alloy. Selected SAC+X alloys have been subjected to thermal shock experiments for crack formation analysis on the copper substrate-solder joints. The results showed that SAC+0.05Al solder has the higher thermal shock resistance, which no cracks were observed after 1500 cycles of thermal shock. In order to understand the insights of SAC performance, some of the lead-free solders were applied onto printed circuit boards for thermal shock resistance test. These results have indicate that the cracking may occur after thermal shock cycles due to process conditions of soldering operation (i.e. cooing rate), independent of the solder alloy composition.
24
Rusen, Aydin. "Recovery Of Zinc And Lead From Cinkur Leach Residues By Using Hydrometallurgical Techniques." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608669/index.pdf.
Full textAbstract:
In this thesis, it was aimed to select and propose a feasible method, or series of methods, for the recovery of zinc (Zn) and lead (Pb) that are present in disposed ÇiNKUR leach residues having 12.43 % Zn, 15.51 % Pb and 6.27 % Fe. Initially, physical, chemical and mineralogical characterizations of the leach residues were done. Results of these analyses showed that lead was present as lead sulfate (PbSO4), and zinc was present as zinc sulfate heptahydrate (ZnSO4.7H2O), zinc ferrite (ZnFe2O4) and zinc silicate (2ZnO.SiO2) in the leach residues. Initially, water leaching experiments were carried out to determine water soluble amount of blended leach residue, and the maximum zinc recovery was obtained as 18 %. After these trials, sulphuric acid and brine leaching were used to recover zinc and lead, respectively. Firstly, due to the insufficient recovery in water leaching trials acid leaching experiments were done for zinc recovery and the parameters studied were acid concentration, reaction duration, leaching temperature and solid-liquid ratio (pulp density). About 72 % Zn was recovered after hot acid leaching by using 150 g/l H2SO4 at 95 oC in 2 hours with a pulp density of 200 g/l. For lead recovery brine leaching experiments were done with the secondary leach residue obtained after H2SO4 leaching. In brine leaching experiments, NaCl concentration, pulp density (solid/liquid ratio), reaction duration and leaching temperature were chosen as variables. Effect of HCl addition was also investigated. In brine leaching while lead recoveries up to 98 % could be attained at a low pulp density in laboratory scale, the maximum recovery obtained was 84.9 % at a high pulp density (200 g/l) with 300 g/l NaCl concentration in 10 minutes at 95 oC.
25
Cunningham, Jock Bernard. "Bulk analysis of lead smelter sinter plant products for sulphur (and Pb, Fe, Zn) using neutron inelastic scatter gamma-rays." Thesis, Queensland University of Technology, 1987.
Find full textAbstract:
A potential for increasing the production in the lead sinter plant at Mount Isa exists if the sulphur and moisture concentration in the feed material could be controlled accurately. This thesis reports on a project to develop an on-line instrument to measure sulphur and moisture in sinter feed for process control. The feasibility of measuring the concentrations of lead,
iron and zinc is also examined. The instrument uses the technique of fast neutron inelastic scatter gamma ray measurement for the element determinations and neutron moderation for moisture measurement.
Three instrument geometries were examined under laboratory
conditions:-
(a) annular
(b) semi-annular
(c) backscatter - main layer
(d) backscatter - ignitor layer
An instrument based on geometry (c)
constructed and tested in the laboratory.
above, was designed, The instrument was shown
to measure sulphur, lead, iron, zinc and moisture to within (one standard deviation) O. 67, 1.2, 0.49 and 0.34 and 0.49 -weight 1.respectively. The repeatability for a aeasurement time of 25 minutes was 0.40, 0. 70, 0.20, 0.17, 0.3 weight 1. respectively. This performance is adequate for process control.
26
Bruce, Scott Lachlan. "Development of a risk assessment tool to minimise the impact of arsenic and lead toxicity from mine tailings /." [St. Lucia, Qld], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18261.pdf.
Full text
27
Lundström, Nils-Göran. "Mortality and morbidity in lead smelter workers with concomitant exposure to arsenic /." Umeå : Univ, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1443.
Full text
28
Sunkar, Ahmet Semih. "Investigation And Development Of Possible Leaching Processes For Recovery Of Zinc And Lead From Cinkur Leach Residues." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605886/index.pdf.
Full textAbstract:
The major aim of this study was to investigate various leaching methods for the recovery of zinc and lead from blended neutral leach residues of Çinkur having a composition of 12.59 % Zn, 15.21 % Pb, 6.45 % Fe, 0.054 % Cd. Initially water leaching tests were performed at various conditions of leaching temperature, reaction time and particle size. The optimized conditions for water leaching were found to be 2 h, 95&
#61616
C and 250 g/l pulp density with a final pH of 5.9. However, the zinc recovery value of 10.26 % was not adequate for industrial scale operations itself. In acid leaching trials
acid concentration, temperature, reaction time and particle size were the chosen variables. At the optimized condition of 150 g/l H2SO4, 95&
#61616
C, 2 h at 250 g/l pulp density with a final pregnant solution pH of 4.2, the extraction values were determined as 74.87 % for Zn and 39.59 % for Fe. These recovery values were evaluated as suitable for industrially feasible operations while creating a secondary leach residue of a composition of 4.10 % Zn, 19.17 % Pb, 5.52 % Fe and 85 ppm Cd that would not be suitable for pyrometallurgical lead production. After recovering zinc in considerable amount by hot sulphuric acid leaching, NaCl leaching experiments for the extraction of lead were done on the secondary leach residue by taking temperature, time and pulp density into account. The most promising conditions of brine leaching for lead recovery were found as 300 g/l NaCl, 20&
#61616
C, 15 minutes and 20 g/l pulp density that gave approximately 82 % lead recovery with a final residue of 7.87 % Pb, 6.86 % Zn, 8.79 % Fe.
29
Christopher, Petersson. "Erosion-Corrosion experiments on Steels in liquid lead and Development of Slow Strain Rate testing rig." Thesis, KTH, Kärnenergiteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261611.
Full text
30
Celtikci, Baris. "Preparation Of Lead-free Bzt-bct Thin Films By Chemical Solution Deposition And Their Characterization." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614623/index.pdf.
Full textAbstract:
In the presented thesis, lead-free Ba(Ti0.8Zr0.2)O3-(Ba0.7Ca0.3)TiO3 (BZT-BCT) thin films were deposited on Pt/TiO2/SiO2/Si substrates using chemical solution deposition method and then the effect of process parameters were investigated to obtain optimum parameters of these lead-free thin films. The phase was selected near to the morphotropic phase boundary (MPH) to increase the number of polarization directions where rhombohedral and tetragonal phases exist together.
In this study, the effect of sintering temperatures on microstructure, dielectric and ferroelectric properties were studied systematically. Among the various high-quality BZT-BCT thin films with uniform thickness, the optimum dielectric and ferroelectric responses were observed for films annealed at 800 oC for 1 h sintering time. The thickness was kept constant for all measurements as 500 nm (triple layered films). Therefore, the average grain sizes were found around 60 nm for samples sintered at 700,750 and 800 oC.
BZT-BCT thin films sintered at 800 oC showed effective remnant polarization and coercive field values of 2.9 µC/cm2 and 49.4 kV/cm, together with a high dielectric constant and low loss tangent of 365.6 and 3.52 %, respectively, at a frequency of 600 kHz due to pure perovskite phase showing full crystallization and minimum surface porosity obtained at this temperature.
31
Ercanli, Levent. "The Examimnation Of Metal Working Technology In Kultepe In Assyrian Trade Colonies Period." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614269/index.pdf.
Full textAbstract:
Metal played important role in the social and economic development of societies since its discovery. It is so important that the some part of humankind historical development were designated by the type of metal which was extensively used depending upon the level of technology of that period enabling the processing of metal like bronze age and iron age.
In this frame, the rich metal deposits of Anatolia made this region a very important metal working and civilization center.
Kültepe where it was the center of the trade organization in Anatolia realized between Assur and Anatolia during 1945-1730 B.C called Assyrian Trade Colonies Period was one of the most important metal working center of Anatolia at that period. In this thesis, it is aimed to make a contribution to understand the metal working technology in Kü
ltepe by examining the uncovered metal artifacts dated to that period. For this purpose, the metal artifacts uncovered from Kü
ltepe Ancient Site belonging to Colonies Period which are exhibited in the Anatolian Civilization Museum were examined by portable XRF (PXRF) to obtain the quantity of elements that constituted the artifacts without giving any harm to the artifact. Besides the examination of exhibited artifacts in the Anatolian Civilization Museum, the uncovered metal artifact parts belonging to Colonies Period which are not suitable for exhibition and separated for studying were examined by energy dispersive X-ray unit of scanning electron microscope for elemental analysis and by X-ray diffraction for the analysis of minerals. The microstructures of artifacts were examined by scanning electron microscope and optical microscope for revealing the operations on metal applied by ancient metalsmith. In addition to analysis mentioned above, in order to make a contribution to understand the copper trade between Kü
ltepe and its environs lead isotope analysis of some samples from the separated metal artifacts for studying was also performed. As a result of all those analyses, it was concluded that Kü
ltepe ancient metalsmiths in Colonies Period had the knowledge to smelt the copper and to pour molten metal into a mold to produce an object of desired shape. Moreover, they also discovered that the addition of some elements to copper hardens the structure. In this frame the bronze to be obtained by deliberately adding of tin to copper was attained. In addition, they were aware of shaping the casted object by hammering. In the meantime, they had the knowledge of heat treatment that allows them forging the object many times till giving the desired shape without causing the fracture in the structure.
32
Stenman, Johan. "Pretreatment Methods for Manganese Containing Anode Sludge." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65751.
Full textAbstract:
This master thesis work examines whether it is possible to separate lead from an electrolytic sludge rich in manganese using pyrometallurgical treatment, and also attempts to determine the optimum process parameters for such a treatment. It also includes a theoretical study of the possible applications for lead and manganese, as well as thermodynamic calculations predicting the behaviour of the material at increasing temperatures. The experimental work completed includes characterisation and agglomeration of the raw material, as well as tests in a chamber furnace and a rotary furnace. The anode sludge was characterised using chemical analysis, XRD, SEM and PSD. The anode sludge was agglomerated into pellets using either both bentonite and water, or only water as binder. The smaller scale tests in the chamber furnace examined the impact of several variables on lead removal. These variables included type and amount of reduction agent used, temperature, and whether the anode sludge was added as untreated material or pellets. The most promising of these results were further tested in the rotary furnace at a slightly larger scale. The variables used for the rotary furnace tests were amount of reduction agent added, whether the anode sludge was added as untreated material or pellets, and whether the reduction agent was added at the start of or during the experiment. All samples were sent for chemical analysis, and selected samples were further analysed using XRD and SEM. The conclusions drawn from the results of the thermodynamic calculations and experimental work are as follows: In the untreated anode sludge the primary phases are MnO2, CaSO4, and (Pb,Sr)SO4. The anode sludge can be agglomerated into pellets, with or without added binder. After treatment the primary phases present are MnO and (Ca,Sr)2SiO4. Lead is present as small separate grains. The most effective treatment method should adhere to the following parameters:Use of a rotating furnace. Anode sludge added in the form of pellets, to simplify materials handling. Temperature of 1400-1500 °C. Reduction agent added in batches after initial smoke formation has stopped. Total addition of reduction agent should be 10 wt% of anode sludge. Significant weight loss occurs during treatment. The amount of reduction agent added to the anode sludge has the greatest effect on the removal of lead and zinc. Charcoal is a potential candidate for a renewable reduction agent, but leads to increased weight loss. It is possible to separate lead from the manganese anode sludge using pyrometallurgical treatment, down to 100 ppm. Zinc can also be separated, down to 600 ppm.Detta examensarbete undersöker huruvida det är möjligt att separera bly från ett anodslam rikt i mangan med hjälp av pyrometallurgiska behandlingsmetoder, och försöker även avgöra de optimala processparametrarna för en sådan behandling. Arbetet inkluderar även en teoristudie av möjliga användningsområden för bly och mangan, samt termodynamiska beräkningar som förutser materialets beteende vid ökande temperaturer. Det experimentella arbetet som utförts inkluderar karakterisering och agglomerering av råmaterialet, samt försök i en kammarugn och en rullugn. Anodslammet karakteriserades med hjälp av kemisk analys, XRD, SEM, och partikelstorleksfördelning. Anodslammet agglomererades till pellets med antingen bentonit och vatten eller bara vatten som bindemedel. Försöken i mindre skala i kammarugnen undersökte hur flera variabler påverkade blyavdrivningen. Dessa variabler inkluderade typ och mängd av reduktionsmedel som tillsattes, temperatur, och huruvida anodslammet som användes var obehandlat material eller pellets. De mest lovande av dessa resultat användes för vidare försök i rullugnen i något större skala. Variablerna som undersöktes vid rullugnsförsöken var mängd reduktionsmedel som tillsattes, huruvida anodslammet som användes var obehandlat material eller pellets, samt huruvida reduktionsmedlet tillsattes vid start eller under försökets gång. Alla prover skickades för kemisk analys, och utvalda prover analyserades ytterligare med XRD och SEM. Slutsatserna som dragits utifrån resultaten av de termodynamiska beräkningarna och det experimentella arbetet är som följande: I det obehandlade anodslammet är de primära faserna MnO2, CaSO4, och (Pb,Sr)SO4. Anodslammet kan agglomereras till pellets. Efter behandling är de primära faserna i materialet MnO och (Ca,Sr)2SiO4. Kvarvarande bly är närvarande som små separata korn. Den mest effektiva behandlingsmetoden bör använda följande parametrar: Användning av en roterande ugn. Anodslam bör tillsättas i form av pellets för att underlätta materialhantering. Temperatur mellan 1400-1500 °C. Reduktionsmedel tillsatt i omgångar efter att initial rökbildningen avstannat. Total tillsats av reduktionsmedel bör vara 10 vikt% av anodslammets vikt. Signifikanta viktförluster under behandling. Mängden tillsatt reduktionsmedel är den faktor som har störst effekt på avlägsnandet av bly och zink. Träkol är en potentiell kandidat för ett förnyelsebart reduktionsmedel, men orsakar ökade viktförluster. Det är möjligt att separera bly från mangan med hjälp av pyrometallurgiska metoder, ned till 100 ppm bly. Zink kan också separeras, ned till 600 ppm.
33
Geindreau, Christian. "Modélisation du comportement viscoplastique des poudres métalliques : simulation à l'aide d'un matériau analogique." Université Joseph Fourier (Grenoble ; 1971-2015), 1996. http://www.theses.fr/1996GRE10169.
Full textAbstract:
L'objectif de ce travail est d'apporter une contribution a la modelisation du comportement des poudres metalliques dans un large intervalle de temperature en utilisant les resultats experimentaux obtenus sous diverses sollicitations avec un materiau modele. La premiere partie de ce memoire est consacree a l'etude bibliographique du comportement des metaux denses dans la gamme de temperature de mise en forme ainsi que des diverses modelisations envisagees permettant de caracteriser les phenomenes plastiques et visqueux observes a ces temperatures. Dans la deuxieme partie, nous presentons differentes lois phenomenologiques utilisees pour les poudres metalliques ainsi que leur comparaison avec les parametres d'un materiau moyen definis a partir des resultats de compression simple et isotrope de la litterature. Pour pouvoir valider ces modelisations, il est apparu necessaire de disposer de resultats experimentaux plus complets sur un meme materiau dans une large gamme de temperatures, de densites et de vitesses de chargement et pour d'autres types de sollicitations que les compressions simple et isotrope. Une vaste etude experimentale a donc ete entreprise avec un materiau modele - le plomb -. La faible temperature de mise en forme de ce materiau a permis de realiser des essais tres varies: compression simple, compactage dometrique avec mesure de contrainte radiale, compactage isotrope et triaxial (150 mpa, 150c) avec mesure en continu de la variation de volume. Le comportement visqueux du materiau ainsi que les phenomenes plastiques qui apparaissent aux vitesses de deformation elevees ont ete mis en evidence. Ces resultats ont ete confrontes aux modeles deja proposes et ont montre l'inaptitude des lois plastiques et viscoplastiques basees sur une loi en puissance. Afin de prendre en compte les effets plastiques et visqueux, le formalisme des lois viscoplastiques unifiees des materiaux denses a ete etendu au materiaux poreux et valide sur les resultats experimentaux en faisant l'hypothese d'un materiau sans ecrouissage. Afin de mieux decrire les differents essais et en particulier les essais dometriques, un nouveau potentiel dissymetrique a ete propose et identifie
34
Bhattacharya, Victoria. "Study Of Friction And Wear Behaviour Of Nano-Embedded Aluminium Alloys." Thesis, Indian Institute of Science, 2000. http://hdl.handle.net/2005/190.
Full textAbstract:
In general, the bearing alloys have two types of microstructure i.e., either a soft matrix with discrete hard particles or a continuous matrix of the harder metal with small amount of the softer metal finely dispersed in it. The aluminium and copper based bearing alloys which are widely studied fall in the second category. However, the bearing materials which have been studied have micron sized dispersoids. In recent times, it is possible to produce nanoscale dispersoids in a hard matrix by the novel processing route of rapid solidification. This offers an opportunity to study the small length scale effect on tribological processes. In this thesis, we deal with aluminium alloys where nanoscaled dispersions of lead, bismuth and indium are produced by rapid solidification processing. Chapter 1 of the thesis is an introduction, followed by Chapter 2, which reviews the literature on nanomaterials. Special attention is given to the monotectic system, followed by a brief description on friction and wear of materials which is necessary for our present investigation. The details of experimental and characterisation techniques are given in Chapter 3. In Chapter 4, we present a brief study of white metal bearings (babbit). Tin-based babbit of composition, Sn-6wt% Cu-llwt% Sb was studied. The study of babbit was mainly carried out with the idea that it could serve as a benchmark for subsequent studies in aluminium alloys, in terms of tribological properties. In particular, we have carried out a detailed electron microscopic investigation on the phases present in the bearing alloy. The friction and wear behaviour of this material confirms the proper calibration of our setup for wear studies. This is followed by a detailed study on the synthesis, microstructure and tribological behaviour of nanodispersed aluminium alloys, Al-6wt% Pb and Al-10wt% Pb in Chapter 5.
For comparison, we have also studied melt-spun aluminium without dispersoids. Detailed electron microscopic characterisation indicates that lead has a cube on cube orientation relationship with the aluminium matrix, and the particles exhibit a lognormal distribution with the mode of the particle size distribution being 15 nm. The pin on disc results suggest a distinct lowering of coefficient of friction corresponding to pure aluminium (μ= 0.40) and as cast aluminium-lead alloys (μ= 0.41). Detailed SEM studies indicate a tribolayer consisting primarily of Al, Pb and Fe. The later comes from the counterface material. Our results clearly indicate that at an early stage, little or no oxidation takes place at the sliding interface. TEM observations indicate significant deformation of lead particles in the sub-surface region. The observations suggest spreading of the lead, which acts as a lubricating layer. Wear behaviour is primarily adhesive and follows Archard's wear law. However, the rate of wear is less than that reported by other investigators on micronsized lead dispersions in aluminium. In Chapter 6, we present the results for alloys dispersed with nanosized indium and bismuth. We show that indium particles on melt-spinning exhibit both cubic and tetragonal crystal structure. The indium particles are coarser (with a mode of 25 nm) than the lead and bismuth particles (which have mode of 15nm). The bismuth containing alloys have a lower wear rate and coefficient of friction compared to lead and indium alloys. However, both indium and bismuth particles do not follow Archard's wear law and the wear vs load graph shows a non-linear behaviour. The results are discussed in terms of known mechanisms of the coefficient of friction and wear. Chapter 7 gives the salient conclusions while in Chapter 8 we discuss some of the unanswered questions and the potential for future work in this field.
35
Dohnalová, Eva. "Vysokoteplotní zkřehnutí feritické 14%Cr ODS oceli v taveninách olova." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229652.
Full textAbstract:
The thesis deals with the high-temperature embrittlement of 14%Cr ODS ferritic steel in liquid lead environment. The 14%Cr ferritic ODS steel ODM401 manufactured by powder metallurgy technology was used as an experimental material. The effect of the long-term annealing, surface corrosion attack in the melt Pb and Pb-Bi on the microstructure and mechanical properties was described. The subsequent microstructural changes were evaluated by means of scanning electron microscopy and transmission electron microscopy The mechanical behaviour of the experimental material was proven by means of microhardness test, impact test and static tensile test. The fractographical evaluation of fracture surfaces were performed on all samples. The surface attack and outstanding microstructural ganges were found after the long-time exposition of the steel in Pb/Pb-Bi melts at temperature 550°C/1000h and 500°C/1000h respectively. The embrittlement of the steel after exposition in Pb/Pb-Bi melts was comparable to the embrittlement after high-temperature annealing of the steel at temperature 650°C/1000h.
36
Lejonklo, Caroline. "Friction and wear study of lean powder metallurgy steel in a lubricated sliding contact." Thesis, Uppsala universitet, Tillämpad materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-390557.
Full textAbstract:
A fairly new technology used to produce metallic components is powder metallurgy (PM). Among the advantages with this technique are decreased cost of production for complex-shaped parts, new alloys are made possible, reduced end processing, less material loss, and vibrational damping effects. The downside is the number of pores created which can alter the tribological properties of the material. The focus of this report is to investigate how lean PM steel behaves under tribological contacts. Friction and wear will be investigated using a pin-on-disc setup to mimic the sliding part of a gear tooth mesh. Previous studies show that the amount of wear, and if the wear increases or decreases with increased density is dependent on the degree of porosity and the pore size. This means that the wear might be minimized by optimizing the number of pores in the material and their shape and size. The result of this study shows that the friction coefficient decreases with increasing density. The wear coefficient show signs of the same correlations but further tests are needed. The main wear comes from adhesive wear, with signs of abrasive wear. The amount of abrasive wear seems to increase with an increase in density, supporting previous studies claiming that pores can trap wear debris and decrease the number of abrasive particles in the contact.
37
Poole, Andrew David. "Development of a lean manufacturing method for the production of metallic fuel pump bearings." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5500/.
Full textAbstract:
The project aim was to develop a lean method for bimetallic fuel pump bearing manufacture using powder metallurgy (PM), as an alternative to flame spraying. Specifically, the sintering and diffusion bonding of aluminum powder alloy to 30% leaded bronze included: • 'Press and sinter': AI-6%Si alloy. 7075 alloy (AI-5.5%Zn-2.5° oMg-1.6%Cu), \(\leq\)500 °C AI-8%Mg-4%Zn alloy, \(\leq\) 500 °C. • HIP (Hot Isostatic Pressing) - AI-6%Si alloy. • 'Hot compaction' - AI-8%Mg-4%Zn alloy. 'Press and sinter' of AI-6%Si alloy resulted in residual porosity and expansion during cooling, due to silicon density reduction during solidification. HIP enabled simultaneous compaction, sintering and diffusion bonding of AI-6%Si alloy to leaded bronze; bearing 'blanks' were manufactured, with an intermetallic layer (approximately 100\(\mu\)m) at the interface.'Press and sinter' of 7075 alloy resulted in swelling during transient liquid phase formation and residual porosity. However, using AI-8%Mg-4%Zn alloy this process demonstrated improvement, as it was closer to its solidus temperature at the chosen processing temperature. Test pieces and bearing 'blanks' were produced, with an intermetallic layer (approximately 20 \(\mu\)m) at the interface, of tensile strength > 20 MPa, superior to flame sprayed bearings. Further work involved optimising HIP and 'hot compaction' processing for batch production.
38
Lora-Soto, Anthony, Cristhoffer Morales-Silva, Jose Llontop-Jesus, and Nestor Mamani. "Process improvement proposal for the reduction of machine setup time in a copper transformation company using lean manufacturing tools." Springer, 2021. http://hdl.handle.net/10757/653764.
Full textAbstract:
This study aimed to identify the causes of significant problems existing in the metallurgical sector, and a solution is proposed for the setup process. We detail the theoretical background of the processes in the lean manufacturing methodology, which will be applied to a rolling machine. Further, we provide a brief description of the company and the sector’s problems. We describe success stories of companies that implemented various lean manufacturing tools. We also present some of the results achieved across sectors to gain an in-depth understanding of the technique and a practical support of the implemented model. Our proposal is based on the lean manufacturing methodology; tools such as Single Minute Exchanges of Dies, Kaizen, 5S, and value stream mapping (VSM) will be used to reduce setup times and to impact machine layout and productivity positively. We also show the implementation results of a pilot plan conducted in the company over a period of more than 3 months.Revisión por pares
39
Gussoni, Rafael. "Implantação de melhorias em uma célula de manufatura de autopeças tubulares, utilizando técnicas da manufatura enxuta." Universidade de Taubaté, 2009. http://www.bdtd.unitau.br/tedesimplificado/tde_busca/arquivo.php?codArquivo=341.
Full textAbstract:
Esse trabalho apresenta uma empresa nacional do ramo metalúrgico fabricante de autopeças tubulares, que implantou conceitos da manufatura enxuta na linha de seu principal produto. A metodologia utilizada foi o mapeamento do fluxo de valor e o levantamento de índices, que refletissem a situação atual no início do trabalho, passando pela análise dos processos produtivos e viabilidade da implantação dos conceitos da manufatura enxuta. Os resultados apresentam uma análise crítica das técnicas implantadas e das melhorias alcançadas, além dos ganhos em produtividade e diminuição das perdas por retrabalhos e refugos dos produtos, melhoria na eficiência dos operadores e melhoria no layout da célula. Foi observada a importância na indústria do conceito de manufatura enxuta, assim como seus resultados positivos frente à expectativa e objetivos gerados no início da implantação.This study shows a national company in the industry Metallurgical, facing the automotive industry that manufactures auto parts and tubes that deployed the concept of lean manufacturing in line of your main product. The methodology began with the mapping of the flow and raising of indices that reflect the current situation, through analysis of processes and feasibility for implantation of the concepts of lean manufacturing. The results presents a critical analysis of developments and improvements achieved, plus the gains in productivity and reduction of rework and scrap products. Are also made suggestions for future studies and projects. In this work we observed the importance of the concept of lean manufacturing in the industry, as well as its positive results compared to expectations generated at the beginning of implantation in order to help further the dissemination of the concept in the industry.
40
Berges, B. J. P. "Acoustic detection of seabed gas leaks, with application to Carbon Capture and Storage (CCS), and leak prevention for the oil and gas industry." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/379746/.
Full textAbstract:
The acoustic remote sensing of subsea gas leakage, applied to the monitoring of underwater gas discharges from anthropogenic and natural sources, is becoming increasingly important. First, as the oil and gas industry is facing increasing regulation, there is a need to put more control in the industrial process and to assess the impact on the marine environment. The applications are diverse, including: early warnings of "blow-out" from offshore installations, detection of leaks from underwater gas pipelines, gas leakage detection from Carbon and Capture and Storage facilities (a process aimed at mitigating the release of large quantities of CO2 in the atmosphere), and seabed monitoring. Second, this technology has a role to play in oceanography for a better understanding of natural occurrences of gas release from the sea floor such as methane seeps. This is of major importance for the assessment of the exchange of gas between the ocean and the atmosphere with application to global warming. All those phenomena involve the formation and release of bubbles of different sizes. These are strong sources and scatterers of sound. Within this context, this thesis draws on a two part study. The first part experimentally addresses the accuracy of a passive acoustic inversion method for the quantification of gas release. Such a technique offers the advantage of lower power requirements for long term monitoring. It is common practice for researchers to identify single bubble injection events from time histories or time frequency representations of hydrophone data, and infer bubble sizes from the centre frequency of the emission. This is well suited for gas release at a low flow rate, involving solitary bubble release. However, for larger events, with overlapping of bubble acoustic emissions, the inability to discriminate each individual bubble injection events makes this approach inappropriate. Using an inverse method based on the spectrum of the acoustic emissions allows quantification of such releases with good accuracy. The inverse scheme is tested using data collected in a large test tank and data collected at sea during the QICS (Quantifying Impacts of Carbon Storage) project. The second part of the thesis addresses the problem of quantifying gas releases using active acoustics. Single beam echosounders are commonly used instruments in fisheries acoustics. When investigating gas release from the seafloor, they are frequently employed to study the spatial distribution of the gas releases. However, few studies make use of these data to quantify the amount of gas being released. Here, using the common multi-frequency ability of these systems, an inverse method aimed at determining gas volumes is developed. This is tested against simulated data and the method shows good performances in scenarios with limited data sets (data collected at limited number of frequencies). Then, using data collected at sea from methane seeps to the west of Svalbard (from two research cruises), the method is applied and compared to independent measurements of gas fluxes.
41
Morales, Silva Cristhoffer Santiago, and Soto Anthony Steven Lora. "Mejora de procesos para la reducción del tiempo de preparación de máquina en una empresa dedicada a la transformación de cobre, utilizando herramientas de lean manufacturing." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2021. http://hdl.handle.net/10757/655683.
Full textAbstract:
El presente trabajo de investigación presenta el análisis realizado para una problemática dentro de una empresa del sector metalúrgico. Se identificaron las causas principales y se propone una solución para el proceso de preparación de máquina (setup). Se detalla la información teórica necesaria para entender los procesos de la empresa en el sector de estudio y la metodología aplicada Lean Manufacturing, la cual fue aplicada en una máquina laminadora. Asimismo, se detalla una breve descripción de la empresa, así como también la problemática del sector. Además, se describen casos de éxito donde fue aplicada distintas herramientas de la metodología que fue empleada en esta investigación con la finalidad de tener una mejor visión de la técnica y un sustento de lo aplicable. Se utilizan herramientas como SMED, KAIZEN, 5S y VSM para reducir el tiempo de setup y lograr un beneficio directamente en la disponibilidad de la máquina y la productividad de esta. Además, se muestra los resultados obtenidos luego de la implementación de un plan piloto dentro de la empresa en un periodo superior a 3 meses. Finalmente, se tiene una discusión sobre los resultados obtenidos frente a similares dentro del área industrial y se visualiza la eficiencia obtenida frente a otras investigaciones.The present work shows the analysis made for a problem within a company in the metallurgical sector. The main causes were identified, and a solution is proposed for the machine preparation process (setup). The theoretical information necessary to understand the processes of the company in the study sector and the applied methodology Lean Manufacturing, which was applied in a laminating machine, is detailed. Moreover, a brief description of the company is detailed, as well as the problems of the sector. In addition, other investigations are described with different tools of the methodology to have a better vision of the technique. Tools such as SMED, KAIZEN, 5S and VSM are used to reduce setup time and directly benefit the machine's availability and productivity. Furthermore, the results obtained after the implementation of a pilot plan within the company in a period exceeding 3 months are shown. Finally, there is a discussion about the results compared to similar ones within the industrial area and the efficiency obtained compared to other investigations is visualized.
Trabajo de Suficiencia Profesional
42
Зырянов, К. Ю., and K. Y. Zyryanov. "Проектное управление модернизацией производственной системы на металлургических предприятиях в концепции бережливого производства : магистерская диссертация." Master's thesis, б. и, 2020. http://hdl.handle.net/10995/86572.
Full textAbstract:
The developed methodology for the modernization of the enterprise’s production system, based on a step-by-step method of managing production processes (6 sigma), the concept of lean manufacturing and statistical data analysis, can be used in projects to modernize the production systems of metallurgical enterprises, increasing their efficiency and competitiveness by: rational use of resources; increase labor productivity; staff involvement. The developed project for the modernization of the enterprise’s production system can be “replicated” at metallurgical enterprises, allowing them to reduce losses, rationally use resources and increase labor productivity. The concept of a project to modernize the enterprise’s production systems using lean manufacturing technologies and project management has found its practical application at the non-ferrous metallurgy enterprise KUZOTsM OJSC.Разработанная методика модернизации производственной системы предприятия, основанная на пошаговом методе управления процессами производства (6 сигм), концепции бережливого производства и статистическом анализе данных, может быть использована в проектах по модернизации производственных систем металлургических предприятий, повышая эффективность их деятельности и конкурентоспособности за счет: рационального использования ресурсов; повышения производительности труда; вовлеченности персонала. Разработанный проект модернизации производственной системы предприятия может «тиражироваться» на металлургических предприятиях, позволяя сокращать потери, рационально использовать ресурсы и повышать производительность труда. Концепция проекта модернизации производственных систем предприятия с использованием технологий бережливого производства и проектного управления нашло свое практическое применение на предприятии цветной металлургии ОАО «КУЗОЦМ».
43
Azizan, Mustapha. "Contribution à l'étude de l'interaction métaux réfractaires (W, Mo, Nb, Ta) - Si(111)(7x7) : [thèse en partie soutenue sur un ensemble de travaux]." Grenoble 1, 1987. http://www.theses.fr/1987GRE10064.
Full text
44
Roger, Francis. "Contribution à la théorie des jets gaz-liquide : application à la modélisation de phénomènes d'érosion-corrosion." Poitiers, 1987. http://www.theses.fr/1987POIT2004.
Full text
45
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
46
Maurice, Vincent. "Contribution a l'etude du desordre dans les monocouches chimisorbees." Paris 6, 1987. http://www.theses.fr/1987PA066518.
Full textAbstract:
Interpretation, a l'aide d'une methode informatisee de type "monte carlo", des diagrammes de diffraction des electrons lents de couches chimisorbees et modelisation des caracteristiques structurales bidimensionnelles liees au desordre. Application au soufre chimisorbe sur des faces de bas indices de metaux de transition
47
"The development of an alternative process for the recovery of lead from sulphide ores." Thesis, 2014. http://hdl.handle.net/10210/8980.
Full textAbstract:
M.Tech. (Minerals Engineering)This report deals with the feasibility study of a novel concept whereby a lead sulphide concentrate and a solid reductant are reacted with a manganese ore at a temperature of approximately lOOO=C. The manganese oxides are reduced to their lower oxides, which, having a higher affinity for sulphur than lead. scavenge the sulphur from the lead sulphide. A manganese sulphide mane is formed. and liquid lead metal is tapped off. The manganese sulphide mane is then leached with sulphuric acid. After a purification step to remove the base metals from solution, the electrolyte proceeds to an electrolytic manganese metal or manganese dioxide facility where the manganese is recovered. The benefits of this process are fourfold: firstly, lead ores may be beneficiated locally; secondly, the separate and often lengthy processes for the recovery of lead and manganese are combined into a simplified process, thereby reducing the capital expense: thirdly, the Leadman process can be applied to any scale of operation: and fourthly, no 502 is produced. Details of the investigation included the following: a literature survey. a laboratory scale study where the operating conditions were narrowed down, a smelting campaign on a rotary kiln, a mineralogical study, a brief leaching study, a leach liquor purification step and a techno-economic assessment. This study has shown the technical and economical feasibility of the Leadman process. The lead and manganese recoveries were both approximately 93%, with good accountability of all the other elements of interest. Depending on the operating conditions, between 80 and 100 per cent of silver, originally in the galena, was recovered with the lead bullion. The purity of the lead metal produced was good with a lead content of approximately 97 per cent, and low levels of contaminants. It was also shown that the manganese matte produced is suitable for use as feed to an existing manganese electrowinning operation. The techno-economic assessment showed a return of R 3 118/t of Pb, compared with R 939/t and R 240/t for the conventional manganese and lead blast processes, respectively.
48
Liu, Cheng-Chung, and 劉振中. "Stress Analysis of Lead-Free Solders with Under Bump Metallurgy for Wafer Level Chip Scale Package." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/20109633855213766610.
Full textAbstract:
碩士國立成功大學
工程科學系專班
91
The wafer level chip scale package (WLCSP) has increasingly become popular due to its wafer-sized compact package. In the WLCSP, the under bump metallurgy (UBM) which connects the solder joint and the chip, is crucial for the package reliability. Additionally, the lead contained in conventional solder joints is adverse to environments and human health, so that many countries are seeking lead-free solder-material for replacement. This study focuses on the WLCSP with lead-free UBM solder joint mounted on the build-up electric board with double-layered micro-via. Finite element analysis ANSYS 6.0 is used for simulations under thermal cycling to investigate the deformations of entire package, micro-via and the changes of stress-vs.-strain hysterisis curve for solder joints. The fatigue life prediction is also included. Three material property theories are adopted, such as viscoplasticity, multilinear isotropic hardening and Garofalo-Arrhenius creep model, to analyze solder joins and compare the differences between results. The complication of this study could give some suggestion to manufacturers the application of lead-free solder joint and UBM, urge them to pay attentions to environmental protections, and furthermore shorten the development period to enhance the competitiveness.
49
Majumdar, Bhaskar. "Thermodynamics And Microstructural Development In Immiscible Systems Processed Through Different Routes." Thesis, 1995. http://etd.iisc.ernet.in/handle/2005/2211.
Full text
50
Vergunst, Thomas Maarten. "The potential for groundwater contamination arising from a lead/zinc mine tailings impoundment." 2006. http://hdl.handle.net/10413/3513.
Full textAbstract:
The mining industry produces vast quantities of overburden and mill tailings. In many instances the disposal of these wastes on the Earth's surface have caused local, and occasionally even regional, water resources to become contaminated. Contamination typically arises from the oxidation of metal sulfide minerals contained within these wastes. Upon oxidation these minerals release sulfate, their associated metal cations and acidity into solution. This study investigated the potential for groundwater contamination arising from a Pb/Zn tailings impoundment in the North West Province of South Africa (Pering Mine). The tailings is composed predominantly of dolomite, which imparts to the material an alkaline pH and a high acid buffering capacity. Acid-base accounting (ABA) established that the capacity of the tailings to buffer acidity surpasses any acid producing potential that could arise from pyrite (FeS2), galena (PbS) and sphalerite (ZnS) oxidation. These minerals account for about 3 to 6% of the tailings by mass. Total elemental analysis (XRF) showed that the material has high total concentrations of Fe (19083 mg kg-I), Zn (5481 mg kg-I), Pb (398 mg kg-I), S (15400 mg kg-I), Al (9152 mg kg-I) and Mn (29102 mg kg-I). Only a very small fraction of this, however, was soluble under saturated conditions. An estimation of potentially available concentrations, using the DTPA extraction method, indicated that high concentrations of Zn (1056 mg kg-I), and moderate concentrations of Pb (27.3 mg kg-I) and Cu (6.01 mg kg-I) could potentially be available to cause contamination. A number of leaching experiments were undertaken to accurately quantify the release of elements from the tailings material. These experiments were aimed at determining the potential for groundwater contamination and also provided a means whereby the long-term release of contaminants could be modelled using the convection-dispersion equation for solute transport. Four leaching treatments were investigated. Two consisted of using distilled water under intermittent and continuous flow, while a third used intermittent flow of deoxygenated distilled water to assess leaching under conditions of reduced oxygen. The.mobilisation of potential contaminants under a worst case scenario was assessed by means of leaching with an acetic acid solution at pH 2.88 (after the US Environmental Protection Agency's toxicity characteristic leaching procedure). The acid buffering potential of the tailings was considerable. Even after 8 months of weekly leaching with 1 pore volume of acetic acid solution the pH of the effluent was maintained above pH 5.90. The protracted acidity caused very high concentrations of Pb, Zn, Mu, Ca, Mg, Hg and S to be released into solution. Leaching the tailings with distilled water also caused the effluent to have noticeable traces of contamination, most importantly from S, Mg, Mu and Zn. In many instances concentrations significantly exceeded guideline values for South African drinking water. Modelling solute transport with the convectiondispersion equation predicted that sol- and Mu contamination could persist for a very long period of time. (±700 years under continuous saturated leaching), while Mg and Zn concentrations would most likely exceed recommended limits for a much shorter period of time (±300 years under the same conditions). In light of the various column leaching experiments it was concluded that seepage from the Pering tailings impoundment could cause groundwater contamination. A drill-rig and coring system were used to collect both tailings and pore-water samples from eight boreholes spread out across the tailings impoundment. These investigations showed that most of the impoundment was aerobic (Eh ranged from +323 to +454 mY) and alkaline (pH 8.0 to 9.5). This chemical environment favours sulfide oxidation and as a consequence high concentrations of S have been released into the pore-water of the impoundment (S concentrations ranged from 211 to 1221 mg r l ). The acidity released as a by-product of sulfide oxidation was being buffered by dolomite dissolution, which in turn was releasing high concentrations of Mg (175 to 917 mg r l ) and Ca (62.6 to 247 mg r l ) into solution. Metal concentrations in the pore-water were low as a result of the strong metal sorbing capacity of the tailings and possible secondary precipitation. The only metal which significantly exceeded recommended limits throughout the impoundment was Hg (concentrations were between 100 and 6000 times the recommended limit of 0.001 mg r l ). Under the current geochemical conditions it is expected that Hg, S and Mg will likely pose the greatest threat to groundwater. The main concerns associated with mine tailings are that of mine drainage and dust blow off..In order to eradicate the latter problem, the tailings impoundment at Pering Mine was covered with a layer of rocks. Modelling the water balance of the impoundment using the computer model HYDRUS-2D showed that the rock cladding has potentially increased the volume of drainage water seeping from the impoundment. In light of the leaching experiments and field work, which proved that water passing through the tailings became enriched with various potentially toxic elements, it is expected that the problem of groundwater contamination around Pering Mine has been further exacerbated by the rock cladding. It was therefore concluded that there would be a strong likelihood of groundwater contamination in the vicinity of the mine.Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.