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1
Govan, Premesh. "Manipulating aqueous chemistry environments in extractive metallurgy." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/10529.
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The Anglo Research Nickel (ArNi) process is a novel extractive metallurgical process that arose out of the need to develop a processing route for the recovery of nickel from lateritic ore deposits that is both economical and environmentally acceptable.
2
Fei, Hong Tao. "Intercritical rolling of a Nb-bearing trip steel." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19663.
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Many engineering materials call for increasing strength and ductility. Unfortunately, the material properties of high ductility and high strength are usually mutually contradictory. These conflicting requirements have generated interest in transformation induced plasticity or TRIP steels, which mainly consist of a mixture bainite, ferrite and retained austenite. The superior strength and ductility of these types of steels is due to the strain induced transformation of retained austenite to martensite. Intercritical deformation (i.e. deformation in the austenite + ferrite two phase region) has been extensively studied on C-Mn and microalloyed steels, but not on TRIP steels. Intercritical rolling increases the volume fraction and decreases the grain size of ferrite. These characteristics may be beneficial to the ductility of TRIP steels, since the volume fraction of retained austenite may increase with ferrite volume fraction by increasing the level of C segregation to the untransformed austenite. As well, the size of the retained austenite may decrease with decreasing ferrite grain size, thus increasing the stability of retained austenite against strain induced transformation. The aim of this study was to investigate the effect of the intercritical deformation on the characteristics of retained austenite and resulting mechanical properties of a TRIP steel.
3
Williams, Katherine E. (Katherine Edith). "An examination of Maya metallurgy, 1150 to 1544 A.D." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/32576.
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Kilic, Arif Nesimi 1963. "A multi-region transient erosion model for concrete with time-dependent surface heat flux." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290695.
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A multi-region, transient concrete ablation and decomposition model is developed. The model consists of four regions of concrete containing a thermally affected region, a dry (evaporated and chemically dehydrated) region, and a gas-free (decarboxylated) region with ablated concrete at the melt/concrete interface. Each region has an interface where the latent heat of local decomposition reactions is taken into account as heat sinks due to endothermic characteristics of the reactions. The time dependent temperature profiles, and depth and growth rate of the regions are evaluated by use of the heat balance integral method. Solutions are obtained for surface heat fluxes in forms of constant, e ⁻(λ)ᵗ, t⁻(λ) and -At to analyze various melt cooldown schemes. The erosion front progresses with a constant rate proportional to the surface heat flux in case of constant heat flux, and terminates at a finite erosion depth that is logarithmically proportional to the cooldown rate for surface heat flux in forms of ⁻(λ)ᵗ and t⁻(λ). Sensitivity analyses are performed to investigate the effects of important thermophysical parameters. Larger erosion depth and rate is observed for higher thermal conductivity. Decomposition temperatures are found to be significant in ablation. Model results were compared with previous experiments and models, and determined to be valid and accurate for different types of melt/concrete interaction. The model presented in this study is simple yet very detailed and accurate in simulating the actual molten core/concrete interaction (MCCI) phenomena, and in investigating the concrete reaction to the molten core. It not only can be embodied into the MCCI codes currently being developed, but also can be used to determine the containment integrity, and fission products released into the environment and to the public as a stand alone code.
5
Krishnaswamy, Sampath. "Weldability of a rapid solidification/powder metallurgy Al-8Fe-2Mo alloy /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu148759874801883.
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Sundaresh, Shlok. "A Mesoscopic Approach Towards Modeling of Compaction Process in Powder Metallurgy." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406225280.
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7
Bulpett, Robert. "The characterisation of white-etching layers formed on engineering steels." Thesis, Brunel University, 1991. http://bura.brunel.ac.uk/handle/2438/4326.
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Metal surfaces, and particularly steels, may be modified by processes which include; plastic-deformation, chemical changes and heating. These layers are often characterised by high hardness and a pronounced resistance to chemical etching. This latter characteristic giving rise to the generically descriptive term "White Layer", which is often applied to such features. Processes which may result in the formation of "White Layer" can be broadly separated into three groups; thermal, chemical and mechanical. In practice, "White Layers" observed on materials removed from service environments have generally experienced a combination of these processes. In this work white-etching layers formed on engineering steels have been characterised, using a variety of electron beam and X-ray analytical techniques, to establish the chemical nature and structural properties of "white layer" material. Specimens drawn from such diverse service applications as; high-pressure tank gun barrels, digger-teeth from gravel extraction plant and adiabatically-sheared armour steel have been compared with samples produced in the laboratory by conventional pin-on-disc wear testing apparatus, specialised machining techniques and laser surface-hardening heat-treatment. The presence of a hard white-etching layer on each of the samples was first established using metallographic examination by light microscopy and microhardness testing to confirm the etch-resistance and high hardness of the white-layer. The chemical composition of the whiteetching layer was then compared with the bulk steel composition using scanning electron microscopy and conventional microprobe analysis ( Z > 11 ), and no significant differences were observed. Light element microprobe analysis and SIMS showed an increase in H, C, N, 0 in the white-etching layers formed within gun barrels, and on abusively turned steel. The levels detected were not considered to be significant in terms of white-layer formation but may well have an influence on strain aging and embrittlement phenomena. A technique for the preparation of cross-sectional thin foils was developed which allowed the structure of the white-etching layers to be compared with the underlying matrix by TEM and electron diffraction. The results of this study showed clear similarities between white-etching layers formed by wear and abusive machining and those formed by adiabatic shear. From these results it is concluded that " white layer " is a fine grain martensite which forms on steel as a result of thermo-mechanical transformation.
8
Ero-Phillips, Olubayode Oladiran. "Development of bi- and multicomponent fibres for tissue engineering by electrospinning." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3587/.
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This project investigated the possibility of tailoring the crystallinity of electrospun fibres (crystallinity studies), and the electrospinning of bi- and multicomponent scaffolds of PLLA. During the crystallinity studies, the effects of various electrospinning process parameters on the crystallinity of electrospun poly(L-lactic acid) (PLLA) fibres were investigated. It was observed that the electrospun fibres had crystallinities between 23 and 46% while that for the as-received granule was 37%, suggesting that the crystallinity of electrospun fibres can be controlled by optimizing the electrospinning process. These results showed that the degree of crystallinity of the electrospun fibres decreased with increasing the polymer solution concentration. Furthermore, an optimum electrospinning voltage at which the maximum degree of crystallinity can be obtained was observed. Finally, bi-component scaffolds based on PLLA and gelatin were electrospun. Multicomponent scaffolds based on PLLA, gelatin and hydroxyapatite (HA) were electrospun followed by electrospraying of the HA phase. Blending gelatin with PLLA resulted in an approximate 50% decrease in fibre diameter. Biocompatibility studies revealed that all scaffolds permitted cell attachment with best results observed on the PLLAGel-HA scaffolds. This was attributed to the exposed HA particles on the surface of the PLLAGel-HA scaffolds which promoted better binding with integrins for osteoconductivity.
9
Kim, Hyoungbae 1969. "Physical modelling of two phase flows in ladle-shroud systems." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20914.
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The onset of a 'late' rotating vortex over an off-centre drain nozzle at 2/3 radius was studied in an 1160-mm diameter tank. It was found that using a sloped bottom ladle could be beneficial in terms of steel yield, provided the exit nozzle is located 'centrically'.Miner modification of the nozzle (skewed nozzle) to impart a radial component of velocity to the spinning vortex core was found to be effective in making AMEPA system sensitive to early slag entrainment phenomena by diverting the core away from the central vertical axis of the nozzle.
A 0.75 scale water model was constructed to simulate the flow of liquid steel through a ladle shroud in the presence of gas infiltration. It was found that the ladle shroud slag detector could be temporarily 'blinded' by gas bubbles or permanently blinded by a standing submerged gas jet.
10
Sum, Maisie. "Variant selection during the austenite-to-martensite transformation." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21328.
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Variant selection rules are described that predict the austenite-to-mariensite transformation textures of an Fe-30% Ni alloy. The occurrence of variant selection is explained in detail using the crystal plasticity model of Bishop and Hill and the Kurdjumov-Sachs transformation relationship. A correlation is established between the slip systems of the former and the rotation axes of the latter. The selection criteria are based on a combination of slip activity, that is, active slip systems defined in terms of positive shears, and permissible dislocation reactions. Thus some of the variants selected are associated with slip systems that are active, while the remainder are accounted for by the in-plane reaction of active dislocations to form inactive or unstressed dislocations. The variant selection criteria are tested against two strain paths; plane strain rolling and axisymmetric compression. Extensive studies were conducted on the former strain path and revealed excellent agreement between the measured and predicted transformation textures. A more detailed analysis is still required for the axisymmetric compression strain path, although, the results obtained indicate that the variant selection model does indeed generate a transformation texture that is consistent with the experimental one.
11
Kim, Hyoungbae. "Modelling of transport phenomena in a delta-shaped, four-strand tundish." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19523.
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A full-scale physical model of a delta-shaped, four-strand tundish was constructed at McGill University to find optimal operating conditions for the tundish. The objective of this work was to determine how best to increase steel production rates by 14% over current tundish operating conditions, these being 12 tons/min with four 15.0 mm outlet nozzles for a 500 mm depth of liquid steel while maintaining steel quality levels. Two options were suggested: the normal head option uses 16.0 mm outlet nozzles and maintains the 500 mm tundish level, while the high head option uses 14.8 mm outlet nozzles and raises the depth of liquid steel within the tundish to 800 mm. The important effects of flow control devices on the hydrodynamic performance of the tundish were also tested, using two different types of flow modifiers: Impact Pad and Turbo-Stop. For a proper comparison between the two options, three aspects were investigated; vortex formation phenomena during tundish draining between ladle changes, Residence Time Distribution (RTD), and Inclusion Separation Ratios (ISR). Inclusion removal rates were studied experimentally with the aid of the aqueous" Liquid Metal Cleanliness Analyzer (LiMCA) system. Particle Image Velocimetry (PIV) was used to visualize the actual instantaneous, or momentary, flows, thereby providing the data needed for time averaged velocity fields and turbulent kinetic energies. A mathematical model based on METFLO was developed to simulate these tundish operations numerically. The Renormalization Group turbulence model (RNG) as well as the standard high Reynolds number k-s turbulence model (STD) was implemented in order to simulate the turbulent flows within the tundish. The validity of METFLO was confirmed by PIV measurements and the numerical predictions of the RTD, and RRI matched the results of physical modelling.
12
Aliravci, A. "Elimination of shrinkage microporosity in magnesium castings by strontium additions." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22409.
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In this study a technique--that almost completely eliminates shrinkage microporosity--has been developed which uses small additions of strontium together with risers and chills to produce porosity-free AZ91C (Mg/Al/Zn) magnesium casting alloy castings. With the optimum level of Sr addition (0.01% to 0.02% Sr), shrinkage microporosity was removed from the casting and concentrated in the riser. The castings were already grain-refined by carbon inoculation. The effect of strontium is explained by a further reduction in the grain size of the castings from 250$ mu$m to 120$ mu$m. This effect produces a much denser casting due to increased mass feeding. In addition, a slow grain growth rate, caused by Sr addition, may keep the liquid intergranular-channel radius large during the final stages of solidification, and results in improved intergranular feeding. Another effect of strontium addition may possibly be attributed to a decrease in the surface tension and viscosity of the liquid AZ91C alloy, which in turn increases capillary feeding of the liquid metal. (Abstract shortened by UMI.)
13
Stephen, Gail. "Al-Fe-Si intermetallics in 1000 series aluminum alloys." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26424.
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Iron and silicon are the major impurities in the 1000 series of wrought aluminum alloys. As the aluminum is recycled, it picks up more and more of these impurities which cannot economically be refined out of the aluminum. When the concentration of these impurities reaches a certain limit (maximum limit in 1000 series is 1 weight percent (Fe+Si)), the aluminum must be downgraded. The Fe and Si form brittle intermetallic phases in these alloys. The two main phases are the plate-like $ beta$-AlFeSi (Al$ sb5$FeSi) and $ alpha$-AlFeSi (Al$ sb8$Fe$ sb2$Si) which has a Chinese Script morphology. The mechanical properties of these alloys are believed to depend largely on the nature of these intermetallics.In the first part of this study, the conditions at which the intermetallics form, along with the ability of strontium to modify them were investigated. The second part consisted of determining how the morphology of the Al-Fe-Si phases affects the mechanical properties of the worked product. It was found that the formation of the Chinese Script morphology is promoted with increasing cooling rates, Fe/Si ratios and additions of strontium. However, the relative amount of Chinese Script was found to decrease with increasing (Fe+Si) levels. Tensile testing and formability testing (Erichsen ball punch deformation test) revealed that the presence of a Chinese Script morphology of Al-Fe-Si intermetallics (as opposed to the plate-like morphology) imparts no significant beneficial effect on the formability of the final rolled sheet.
14
Kondos, Peter Dimitri. "Pressure chloride leaching of a complex URaNiAs ore : statistical modelling and solution chemistry." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28405.
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The solution chemistry and statistical modelling of the O$ sb2$-CaCl$ sb2$-HCl leaching of a high-grade arseniferrous uranium ore (Key Lake, N. Saskatchewan) were studied with the objective of optimizing the co-extraction of uranium and radium. To this end, two types of experiments were carried out: (a) those designed to study arsenic speciation under simulated U-leaching conditions, with the use of model arsenide minerals, namely niccolite (NiAs), rammelsbergite (NiAs$ sb2$) and gersdorffite (NiAsS); and (b) statistically designed tests involving actual leaching of samples of the Key Lake ore.Niccolite and rammelsbergite were found to yield H$ sb3$AsO$ sb3$ in solution as oppossed to gersdorffite, which was found to yield H$ sb3$AsO$ sb4$. H$ sb3$AsO$ sb3$ was found to be metastable in the Fe$ sb2$(SO$ sb4) sb3$ leaching system, while in the FeCl$ sb3$ and pressure (O$ sb2$) leaching systems, further oxidation to H$ sb3$AsO$ sb4$ was observed to take place at relatively slow rates. A mechanism has been advanced to account for the latter slow oxidation of H$ sb3$AsO$ sb3$ to H$ sb3$AsO$ sb4$. Finally, it was concluded that the formation of As(III)/As(V) in oxidative acid leaching is independent of the prevailing suspension redox potential which, in turn, renders impractical the possible stabilization of As(III) via potential control.
The solubility of RaSO$ sb4$ in HCl-MeCl$ sb{ rm x}$ leaching media was quantitatively established by employing the "reduced activity coefficient" method. The estimated solubility profiles clearly demonstrated the effectiveness of CaCl$ sb2$ in solubilizing radium as oppossed to other monochloride salt additions.
Finally, optimization of the co-extraction of U and Ra was attained with the use of a computer-aided response surface methodology. An incomplete three-level, four-variable factorial design (Box-Behnken) was applied in the region: 0.33 kg/L $ leq$ d$ sb{ rm s}$ $ leq$ 0.99 kg/L; 0.5N $ leq$ (HCl) $ sb{ rm o}$ $ leq$ 1.5 N; 1.5 M $ leq$ (CaCl$ sb2 rbrack sb{ rm o}$ $ leq$ 3.5 M; and 2 hrs $ leq$ Time$ leq$ 6 hrs. Temperature and oxygen pressure were kept constant at 68$ sp circ$C and 510 kPa (75 psi), respectively. Uranium and radium were found to dissolve simultaneously and rapidly (99% co-extraction in 2 hrs). Effective reduction of radioactivity levels from 10,000 pCi/g Ra$ sp{226}$ down to 160 pCi/g has been achieved in a single-stage batch process, thus making possible the production of environmentally innocuous tailings.
15
Lobel, Jonathan. "The direct recycling of dust generated in the electric arc furnace stainless steelmaking process /." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33335.
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This research investigates the possibility of recovering the metallic content of the dust generated by stainless steelmaking operations in the Electric Arc Furnace (EAF) at ATLAS Stainless Steels by recycling it to the EAF. The physical and chemical properties of the dust were determined. The pelletization of dust-carbon fines was optimized in order to obtain strong pellets capable of carbothermic self-reduction. The high temperature behavior of dust-carbon pellets was investigated in a Thermogravimetric Analyzer (TGA) coupled with a Fourier-Transform Infrared Spectrometer (FTIR). The mechanisms involved in metal recovery were identified. The feasibility of direct recycling was verified by testing pellets in a scaled-down simulation of the EAF process. As a result of this research practical recommendations concerning the application of the direct recycling process at ATLAS were formulated.
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Ng, Ka Wing 1965. "Skimming of fluid slag." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33340.
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A 1/12 scale tank was constructed to physically simulate the metallurgical skimming process in order to gain a better insight of the skimming of fluid slag from copper anode furnaces. 1-decanol and water were used to represent the slag and the underlying liquid metal respectively. It was observed that slag skimming was comprised of two steps, a transportation step to carry slag to the skimming lip, and a removal step to move the slag across the lip. The efficiency of the transportation by bath surface circulation was strongly affected by the method of creation of the surface movement. Submerged gas injection failed to carry slag to the lip effectively because of the uncontrollable circulation pattern generated on the bath surface. On the other hand, three impinging gas jets in glancing contact with the bath surface were able to carry slag to the lip effectively. The Re of the jets (I.D. 0.01m) inclined 50° to the horizontal was 6100. The jet configuration was two of the jets were placed close and parallel to the rear wall of the model and faced each other. The third jet was parallel to the model short axis and was directed at the skimming mouth. With the same amount of time, 70% of the slag originally charged to the tank was skimmed with the assistance from the impinging gas jets in comparison to 20% when no jet was used. Detailed analysis of the skimming process revealed that the underlying liquid bath level continuously decreased as the slag was skimmed and resulted in continuous reduction of the skimming rate. In order to compensate the reduction of skimming rate due to bath level reduction, a control strategy was proposed for rotating the furnace continuously to maximize the skimming effectively.
17
Larouche, Pascal. "Minor elements in copper smelting and electrorefining." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33978.
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Minor element (As, Sb, Bi, Pb, Ni) behavior, control and removal techniques in the conventional copper smelting/electrorefining process was studied. The analysis was based on the information collected from an exhaustive literature review, the visit of 23 smelters, 14 electrorefineries and consultations at 15 different institutes specialized in the field.Data was collected for several types of matte smelting furnaces such as Outokumpu flash, INCO flash, Mitsubishi S-furnace, Teniente Converter, Noranda Process Reactor, Isasmelt and reverberatory. Behavior in Peirce-Smith converting furnaces, Mitsubishi C-furnace, Noranda Continuous Converter and Kennecott-Outokumpu Flash Converting Furnace was also discussed.
The effect of various matte smelting furnace operating parameters such as matte grade, oxygen enrichment, concentration in feed, other minor constituents and temperature on minor element partition to gas and distribution coefficient (wt% matte/wt% slag) was analyzed theoretically and validated with industrial data when possible. Because fewer data were available, only a brief comparison between the elimination in traditional batch converting and new continuous converting processes was performed. The behavior of minor elements in electrorefining was described from a theoretical viewpoint. (Abstract shortened by UMI.)
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Naji, Meidani Ali Reza. "A study of bubble dynamics and some metals processing applications /." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38086.
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In this research the dynamics of a non-reactive and a reactive gas bubble under various pressure fields are studied. Comprehensive mathematical models have been developed to simulate the dynamic behavior of different gas bubbles. On the basis of these models several features of thermo-fluid mechanical behavior of gas bubbles are then discussed and their applications for the metals processing operations are described. The mathematical models form a set of coupled, highly nonlinear and stiff differential equations, which have been solved numerically by a modified Gear method.The first part of this study is concerned with the transient dynamic behavior of a hydrogen gas bubble in a solidifying aluminium-3.4 wt pct copper alloy melt under various ultrasonic pressure fields. During the process of bubble collapse, the melt pressure surrounding the bubble is seen to increase very rapidly. The variations of pressure and supercooling in the melt surrounding the bubble can cause bulk crystallization. If the pressure in the vicinity of the dendrites exceeds a threshold value, dendrite fracturing takes place. Dendrite fragments become nuclei during metal crystallization in an ultrasonic field, which lead to the refined crystalline structure of the metal. The results show that adjacent to the bubble surface, the peak pressure generated in the melt is in the order of several hundreds to thousands atmospheres depending on the initial bubble size, pressure of undisturbed melt and the ultrasonic's specifications.
The second part of this study is related to the dynamics of a stable bubble under various ultrasonic pressure fields. When the imposed pressure field is beyond a threshold value, dissolved gas in the liquid flows into the gas bubbles by rectified diffusion. In this case, the bubbles grow sufficiently to float to the surface due to the hydrodynamic buoyancy force. The results show that the air bubble grows and the time-averaged bubble volume reaches several times of its initial value when the ultrasonic pressure amplitude is more than the threshold pressure.
The final part of this study consists of the complex dynamic behavior of a reactive gas bubble immersed in a nonreactive liquid under various liquid impulse pressures. Numerical investigations are conducted into the collapse and explosion of an isolated oxygen-hydrogen bubble immersed in water and in glycerin. The results show that, if the imposed pressure field is strong enough, the bubble is seen to explode. (Abstract shortened by UMI.)
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Nickoletopoulos, Nicholas. "Physical and numerical modeling of steel wire rod fracture during upsetting for cold heading operations." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37796.
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A comprehensive methodology to physically and numerically model upsetting in cold heading was developed.The physical model was a Drop Weight Test with a guided pocket-die set capable of approximating industrial cold heading conditions. The results show that the test is sensitive to the critical parameters for cold heading. These include surface quality, residual element level, nitrogen content, microstructure, decarburization, and specimen geometry. The test is capable of assessing the fracture behavior of cold heading materials.
One goal of the study was to reveal differences in fracture behavior with varying steel sources. Accordingly, the matrix of test materials consisted of grade 1038 steels from three different steel sources.
Material preparation and conditioning of test materials approximated industrial procedures for cold heading materials. These procedures included hot rolling, controlled rod cooling, descaling, straightening, lime coating and lubricating, and wire drawing. Spheroidization of test specimens was performed in an industrial batch furnace using an industrial heat treatment cycle.
A finite element program (FEM) enabled the simulation of upsetting in cold heading. The inputs required to model the cold heading process include flow stress behavior and friction conditions representative of cold heading. These inputs were obtained using the CANMET Cam Plastometer and the Friction Ring Test.
The Cockcroft and Latham fracture constants for an as-rolled and a spheroidize annealed 1038 material were computed by FEM modeling and the critical values were calibrated using the Drop Weight Test. The fracture criterion constant was found to be independent of strain path for upsetting in cold heading and thus is material-related.
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Noaparast, Mohammad. "The behaviour of malleable metals in tumbling mills." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40217.
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The objective of this work was to investigate the behaviour of malleable metals in tumbling mills. Much of the work focused on lead: shots, flattened shots and fragments were ground in three different laboratory mills. Testwork with fragments was repeated in the presence of a brittle and harder mineral phase (95% silica, 5% lead) and for copper (100% copper). The transfer of particles across size classes and the loss of weight because of smearing on the mill shell and grinding media were measured. Microhardness tests confirmed that lead did not work-harden during grinding.The transfer across size classes was modelled with various first order differential equations describing flattening, folding, cold-welding and actual breakage. Model parameters were estimated using a least-square minimization criterion. When more than one model was fitted to a given data set, the one whose phenomenological basis was closest to the dominant transfer mechanisms observed almost always yielded the best data fit. The dominant mechanism was very dependent on the type of metal ground, its particle size and shape, the grinding intensity generated by the tumbling mill and the presence of a hard, brittle phase. Flattening, responsible for the transfer to coarser size classes, generally dominated over folding, the mechanism accountable for the transfer to finer size classes (other than breakage). Breakage was favoured over flattening and folding when grinding finer and softer particles,in a high impact environment, or in the presence of a hard, brittle mineral phase. Loss of weight due to smearing significantly increased when grinding a softer mineral in a mill with a rough inner shell, or when particle breakage took place.
A methodology based on the Laboratory Knelson Concentrator was developed and tested to estimate the breakage function and gravity recoverability of gold flakes. Progeny from the breakage of gold particles was shown to be highly gravity recoverable, more than 90% above 0.025 mm. The breakage function was non-normalizable, with a large b$ sb{ rm i+1,i}$ component, because of folding.
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Aboutalebi, M. Reza. "Modelling of turbulent transport phenomena and solidification in continuous casting systems." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41514.
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A numerical modelling study has been undertaken to analyze transport phenomena in various steel casters. During the course of this work, a general three-dimensional parabolic heat flow model was developed for casters of arbitrarily shaped mould using a body-fitted coordinate transformation technique. The heat flow model was specifically applied to a beam blank caster as well as to an industrial slab caster of regular rectangular cross section, so as to analyze solidification within casters.Furthermore, a fully coupled turbulent flow and solidification model was developed to describe the turbulent transport processes in the upper part of a steel slab caster as well as to evaluate the process variables affecting the casting. Solidification modelling was carried out using a fixed grid enthalpy method while the mushy zone was modelled based on a Darcy-porosity approach. A modified low-Reynolds number version of the $ kappa$-$ epsilon$ model of turbulence was employed to calculate eddy viscosity within the liquid and mushy regions. A control volume based on finite difference method was used to solve the transport equations, wherein a SIMPLER algorithm was adopted to resolve the velocity-pressure coupling in the momentum equations. In order to verify the turbulent flow model, a water modelling study was performed for fluid flow in the mould region of a slab caster. Reasonable agreement was obtained between the mathematical model's predictions, and water modelling experiments.
Macrosegregation of carbon in a steel billet caster was also modelled based on a continuum formulation, in which the conservation equations are derived in terms of mixture dependent variables. The effect of turbulence on the transport of solute in the liquid and mushy regions was taken into account using the $ kappa$-$ epsilon$ model adopted in this work.
Various parametric studies have been preformed on different casting systems, and their effects on temperature distributions and velocity fields within the strand, solidification profiles, and trajectories of inclusions were predicted. Typical predicted results of the models have been compared against the experimental measurements on operating casters reported in the literature and relatively good agreement was obtained.
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Paray, Florence. "Heat treatment and mechanical properties of aluminum-silicon modified alloys." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41146.
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The commercial applications of cast Al-Si alloys depend to an important extent on controlling the morphology of the eutectic silicon through thermal modification in the solid state and/or chemical modification of the melt before the production of the casting. The effects of modification and/or heat treatment on the microstructure and the mechanical properties of 356 alloy have been investigated on both permanent mold and sand cast samples. Strontium (0.02%) and sodium (0.01%) were used to produce well modified microstructures. The importance of the amount of modifier used was also examined in producing castings with 0.002% Sr and 0.08% Sr. Production parameters such as solution heat treatment time and artificial aging time were examined.Microstructural assessment was done by quantitative metallography using image analysis coupled to SEM while mechanical testing comprised tensile testing, hardness and microhardness measurements as well as impact tests.
The greatest improvement in mechanical properties obtained with modification was observed for the lower rates of solidification, i.e sand casting. The effect of modification on the heat treatment response of 356 alloy was investigated. The differences between unmodified and modified microstructures were more important in sand cast samples than in permanent mold cast samples. After one hour of solution heat treatment at 540$ sp circ$C, both permanent mold unmodified and modified microstructures became similar in terms of silicon particle size and sphericity. The processes which led to this were different. Silicon platelets in the unmodified structures segmented while silicon particles in the modified alloy coarsened. The final result was however the same. In sand cast alloy, the initial microstructural differences persisted after up to 12 hours of solution treatment. The coarser the initial as-cast microstructure, the greater the improvements associated with modification and heat treatment.
It was also found that porosity caused by modification can negate many of the microstructural benefits by decreasing tensile strength and percent elongation. It was demonstrated that modification also has an influence on the aluminum matrix. The hardness of modified alloy was found to be less after the T6 temper than in unmodified alloy. This was reflected in a lower yield strength of modified 356 alloy.
Quantitative microstructure-mechanical property relationships were established for the permanent mold samples. The best silicon-structure characteristics to predict the tensile properties were found to be the particle count per unit area and the particle area.
It was also determined that hardness can be a simple and inexpensive means whereby ultimate tensile strength and yield strength of 356 alloy in the T4 condition or T6 condition can be estimated.
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Verhelst, Dominic. "Physical modelling of gas stirred metallurgical reactors containing two liquids." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59908.
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The present work represents a study of the mixing and slag entrainment behaviour of metallurgical processes. Two immiscible fluids were mixed in a model reactor, equipped with a single centrally located tuyere, through which air was blown.For low energy input systems, it was found that the thickness of the second liquid phase can significantly affect the mixing time of the bulk phase by altering the fluid flow pattern of the liquid. The entrainment of the upper phase into the lower phase was also affected by the thickness of the upper phase, as well as by the intensity of bath agitation. At low flowrates, the number density of entrained droplets was constant with time, increasing with increasing agitation and thickness of the layer. The air flow required for the transition in the entrainment behaviour increased with an increase in the thickness of the upper phase.
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Tian, Chenguo. "On the removal of non-metallic inclusions from molten steel through filtration." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59991.
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Non-metallic inclusions in steel such as alumina, silicates, etc. are detrimental to many steel properties. Elimination of these inclusions has long been a major target in steelmaking.In this investigation, attempts have been made to remove these non-metallic inclusions by passing the liquid steel through a ceramic filter. It was found that this approach is very effective for removing solid non-wetting inclusions such as alumina. It appeared that liquid silicates could also be removed to some degree.
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Joenoes, Ahmad T. (Ahmad Taufik). "The role of magnesium on eutectic silicon microstructure /." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60473.
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To improve the mechanical properties of the most widely used Al-Si foundry alloys, small amounts of magnesium are often introduced. However, the effect of magnesium on the eutectic microstructure is unclear. The aim of the present work is to investigate the effect of magnesium on the eutectic microstructure and to clarify its role in the silicon solidification.Experiments were performed on hypoeutectic and eutectic alloys (Al-7%Si, Al-11%Si, Al-13%Si and 413.2 alloys). Assessment of the eutectic microstructure was done using thermal analysis and metallography. The silicon phase was quantified by image analysis in terms of its perimeter, shape factor and aspect ratio. The results reveal that in hypoeutectic and eutectic synthetic alloys magnesium decreases the homogeneity of the microstructure. At about 1%Wt Mg, however, magnesium refines slightly the silicon phase. It was found that magnesium has a negative effect on strontium modification, that is, it changes the microstructure from well modified to partially modified. This is believed due to the presence of a complex intermetallic compound $ rm(Mg sb2SrAl sb4Si sb3)$ formed prior to the eutectic transformation. It is suggested that magnesium not be added in excess of 0.6 Wt% in strontium modified Al-Si alloys.
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Boliński, Lech. "Platinum and rhodium recovery from scrapped automotive catalyst by oxidative acid chloride leaching." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60573.
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There is a great interest in the treatment of spent autocatalyst because, due to large amounts of PGM used by catalytic converters, the autocatalyst scrap is the largest and constantly growing source of PGM available for recycling. A hydrometallurgical method of PGM extraction from honeycomb type catalyst containing platinum (800-1200 ppm) and rhodium (50-60 ppm) using HCl-AlCl$ sb3$-HNO$ sb3$ or HCl-HNO$ sb3$ mixtures was studied. Experimental results of the leaches performed in a bench scale tubular reaction with recycled continuous flow of the leaching solution as well as 1000 cc stirred reactor are presented. The results suggest that Cl$ sp-$ single ion activity plays a decisive role in controlling the PGM dissolution. The extent of PGM recovery increased not by increasing HCl concentration to very high levels, but by keeping a relatively low total Cl$ sp-$ level (2.5 M) with a significant proportion present as AlCl$ sb3$. Rhodium extraction was always 5-10% lower than platinum, and it appears that increasing the AlCl$ sb3$/HCl ratio tends to increase rhodium recovery. High temperature (85-95$ sp circ$C) and an HNO$ sb3$ concentration around 3-3.5 M play very important roles in effectiveness of PGM extraction. The presented method of HCl-AlCl$ sb3$-HNO$ sb3$ tubular reactor leaching supplemented by solvent extraction (Kelex 100) of PGM from pregnant solution appears to be very attractive for small size (5-20 tonnes of catalyst/day) installations.
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Tavernier, Philippe. "Modeling of recrystallization textures." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61775.
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Morales, Franklin R. "Magnesium and calcium rod injection for desulphurization of steel and hot metal." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61923.
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Kuan, Seng How. "The effect of solids on gas holdup, bubble size and water overflow rate in flotation." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66674.
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This thesis reports the effects of solids (hydrophobic and hydrophilic) on gas holdup, bubble size and water overflow rate with different frother types in a continuous flotation column setup. Four frothers were investigated: F150, 1-pentanol, 1-heptanol and DowFroth 250. The gas holdup, bubble size and water and solids overflow rate were measured as solids were added to the gas-water system. Solids used were talc (hydrophobic) and silica (hydrophilic). Measurements were taken at fixed froth depth and gas velocity. The following was found when talc was added: F150 - gas holdup decreased while bubble size increased; 1-pentanol - gas holdup increased while bubble size remained the same; gas holdup and bubble size remained the same with 1-heptanol and DowFroth 250. When silica was used as solids, no significant changes were observed in bubble size and gas holdup with all frothers tested. The observed behaviour of gas holdup and bubble size with F150 upon addition of talc is attributed to two factors: adsorption of frother by talc (an indirect effect) and talc promoting coalescence (a direct effect). The observed behaviour of gas holdup and bubble size with 1-pentanol upon addition of talc can be attributed to talc loading and slowing the rise velocity of bubbles which unlike the case with the other frothers, have not reached terminal velocity. Water overflow in 3-phase talc systems with 1-pentanol, 1-heptanol and DowFroth 250 increased with the addition of talc but in the case for F150 it fluctuated around an approximately constant value. Test results seem to show that the water overflow rate ranking for frothers in 2 phase is reversed in 3 phase with talc. Recommendations were made for future work.L'on rapporte les effets de solides (aussi bien hydrophobiques que hydrophiliques) sur la rétention de gaz, la taille de la bulle, la vitesse d'écoulement du trop plein d'eau, par usage de différents types de moussants dans une colonne de flottation continue. Quatre moussants étaient étudiés: le F150, le pentanol-1, l'heptanol-1 et le DowFroth 250. La rétention du gaz, la taille de bulle et la vitesse d'écoulement du trop plein d'eau et des solides étaient mesurées en même temps que l'on procédait à l'ajout des solides dans le système gaz-eau. Les solides utilisés étaient le talc (hydrophobique) et la silice (hydrophilique). Les mesures étaient prises à des hauteurs de la mousse et à la vitesse du gaz determinées. Les résultats suivants étaient obtenus lorsque le talc était ajouté: pour le F150; la rétention du gaz avait diminué tandis que la taille de la bulle avait augmenté; pour le pentanol-1; la rétention du gaz avait augmenté alors que la taille de la bulle était invariable; pour l'heptanol-1 et DowFroth 250; la rétention de gaz et la taille de la bulle était restées inchangées. Lorsque la silice était utilisée, aucun changement majeur n'était observé, ni pour la taille de la bulle, ni pour la rétention du gaz et ce pour tous les types de moussants testés. Les changements observées pour la rétention de gaz et la taille de la bulle lors de l'utilisation du F150 comme moussant sont attribués à deux facteurs: l'adsorption du moussant par le talc (effet direct) et le talc qui fait la promotion de la coalescence (effet indirect). Le comportement observé dans la rétention du gaz et la taille de la bulle avec l'usage du pentanol-1 est dû à l'accroissement de la masse du talc qui ralentit du coup la vitesse de la bulle, laquelle à la différence des autres moussants, n'a pas encore atteint sa vitesse terminale. L'écoulement du trop plein d'eau dans le systè
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El-Ammouri, Elias G. "Hafnium solvent extraction from chloride solutions using organophosphorus reagents (Cyanex 923, 925)." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69792.
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A comparison of hafnium solvent extraction from hydrochloric acid solutions using either Cyanex 923 or 925 (organic extractants) diluted in kerosene was established. Since understanding of the hafnium-hydrochloric acid solution is important, development of a speciation diagram for such a solution was carried out. While both Cyanex 923 and 925 are mixtures of trialkyl phosphine oxides, the trialkyl group in the former have straight chains, while those in the latter have branched chains.Experimentally, the major variables studied were hydrochloric acid, hafnium and Cyanex concentrations. Hafnium is rapidly loaded as the tetrachloride complex by a solvation reaction forming a disolvate with the extractant (923 or 925). While extraction increases with increasing acid concentration, it decreases with increasing hafnium concentration due to polymerization. Total chloride level is the controlling factor provided there is enough acid to prevent hafnium hydrolysis and polymerization. Cyanex 923 is a more powerful extractant than Cyanex 925 for given conditions. A few experiments have shown that a very dilute hydrochloric acid solution is suitable as a stripping agent.
The main objective is to evaluate the potential of Cyanex 923 (or 925) as an alternative to MIBK due to the problems associated with the latter. MIBK is the conventional extractant for hafnium and zirconium extraction and separation from hydrochloric acid/thiocyanate solutions. Thus, preliminary studies of hafnium and zirconium (existing separately or together) extraction from hydrochloric acid/thiocyanate solutions were also performed. When existing separately, hafnium and zirconium are similarly extracted into either Cyanex reagents, but when both metals coexist in the same solution, preferential separation of hafnium is observed.
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Holcroft, Gillian L. (Gillian Louise). "Dynamics of the jarosite conversion process." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=69798.
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Canadian Electrolytic Zinc in Valleyfield, Quebec utilizes the conventional Roast-Leach-Electrowin process to produce zinc metal. Iron removal is carried out in the jarosite conversion circuit which consists of ten continuous stirred tank reactors in series.In this study, the first five tanks of the jarosite conversion circuit were piloted and process identification experiments were carried out. Step changes in the flows of the raw acid, spent acid, jarosite slurry and zinc ferrite slurry streams were performed. The goal of these experiments was to collect transient response data which could be used to validate a dynamic conversion circuit model. The process was found to be most sensitive to changes in the flow of the raw acid stream.
The zinc ferrite dissolution rate constant calculated from the experimental data agrees with literature values. Using a jarosite precipitation rate expression from the literature, it was found that jarosite precipitation is negligible in the first reactor but cannot be ignored in the second tank.
The dynamic model provides a good representation of the first two tanks of the jarosite conversion circuit and can be used for both process control and optimization studies on a full-scale facility.
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Stewart, Gregg Ryan. "Static and dynamic aging and softening in 304 stainless steel." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84847.
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Interactions between diffusing impurity atoms and dislocations can occur during or following the deformation of metals. These interactions cause dislocation pinning, leading to strain aging. At lower temperatures (<400°C), the relevant solutes are interstitial (in particular, carbon and nitrogen). At higher temperatures (>800°C), substitutional impurities are expected to be most influential. The same mechanisms that result in the yield drops, increased flow stresses and increased work hardening associated with strain aging at low temperatures should result in significant modification of recovery and recrystallization behaviour at higher temperatures.The present work involves the deformation of austenitic (304) stainless steel at high temperatures (800°C to 1280°C) in 1-hit and 2-hit high-temperature compression and multi-hit hot torsion testing. Experimental variables include the strain rate, temperature and interpass time.
Significant anomalies in the static softening kinetics are observed; under certain deformation conditions, the normal relationship between temperature and fractional softening is reversed. This effect is attributed to the non-equilibrium segregation of phosphorus during the interpass holding time. Analysis of dynamic recrystallization (DRX) in the material has revealed retardation of the initiation of recrystallization; this effect is explained in terms of the segregation of substitutional elements to the boundaries of new DRX grains.
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Araya, Ledezma Rodrigo. "Gas distribution in industrial flotation machines: a proposed measurement method." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86957.
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Flotation is a multivariable process that can be considered the output of at least four interacting factors: chemical (frother, collector), physical (particle size, percent solids), machine and circuit arrangement. These factors combine with the aim of producing the best conditions for particle collection.Gas dispersion defines the characteristics of a bubble population generated from a continuous stream of air. Gas Dispersion parameters include superficial gas velocity, gas holdup, bubble size and bubble surface-area flux. Gas distribution defines the spread of the air bubbles throughout the cell volume. It is intuitive that best metallurgical results are likely associated with uniform distribution of gas. The measurement of gas distribution is the focus of this thesis, achieved by simultaneous measurements of gas velocity at several radial distances at a common depth in flotation cells. A distribution deviation index (DDI) is proposed to quantify the distribution.
La flottation est un processus multivariable que l'on peut considérer le résultat d'au moins quatre facteurs : le produit chimique (moussant, collecteur), les aspects physiques (taille des particules, proportion de solides), l'équipement disponible et le circuit de flottation. Ces facteurs se réunissent pour produire les meilleures conditions pour la séparation de particules.
La dispersion du gaz définit les caractéristiques d'une population de bulles produites dans un courant continu d'air. Parmi les paramètres de dispersion, il y a la vitesse superficielle du gaz, la charge gazeuse, la taille des bulles et le flux de superficie des bulles. La distribution du gaz définit la diffusion des bulles d'air partout dans le volume d'une cellule de flottation. Il est intuitif de croire que les meilleurs résultats métallurgiques seraient associés à une distribution uniforme du gaz. La mesure de la distribution du gaz est le sujet de cette thèse, réalisée par mesures simultanées de vitesse du gaz à plusieurs distances radiales à une profondeur commune dans une cellule de flottation. On propose un indice de déviation de distribution (DDI) pour évaluer quantitativement la distribution du gaz.
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Lagno, Felipe. "Encapsulation of scorodite particles with phosphate coatings." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85929.
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Arsenic disposal is one of the most important environmental issues the mining and metallurgical industries are faced with. This problem has worsened in recent years because of the increasing arsenic content of the low-grade and complex ores currently processed by the mining industry and the introduction of stricter environmental regulations.This Ph.D. thesis sought to develop a novel concept for arsenic fixation suitable for the long-term safe disposal of arsenic generated and disposed by the minerals industry. In particular this research project investigates the encapsulation of scorodite, a well characterized Fe(III)-As(V) compound having the following formula FeAsO4·2H2O, with phosphate coatings, materials potentially not prone to reductive decomposition. Reductive decomposition is known to be responsible for the release of arsenic into the environment form arsenate solids such as scorodite.
The subject matter of this thesis is the application of heterogeneous crystallisation techniques to produce stable phosphate coatings on scorodite particles. The experimental work reported in this thesis involved three different types of studies, namely (1) production of a number of synthetic minerals; (2) evaluation of their stability; and (3) encapsulation of scorodite with two of these synthetic minerals. The synthesis work involved the production of aluminium and calcium phosphates via homogeneous, heterogeneous and seeded crystallisation. The stability work involved the study of the dissolution of hydrated aluminium phosphate (AlPO4·1.5H2O), dicalcium phosphate dihydrate (CaHPO4·2H2O), and calcium-deficient hydroxyapatite (Ca10-x(HPO 4)x(PO4)6- x(OH)2-x, x <2). Finally, the encapsulation work involved the deposition of hydrated aluminium phosphate and calcium-deficient hydroxyapatite on scorodite particles and the evaluation of their stability in simulated oxic and anoxic environments.
The directed deposition of phosphate on scorodite particles was achieved via the control of supersaturation. For the directed deposition of aluminium phosphate, the supersaturation was controlled via pH adjustment. On the other hand, for the controlled deposition of calcium-deficient hydroxyapatite on scorodite particles supersaturation was controlled via regulated mixing of two Ca(II) and P(V) solutions at constant pH. Both encapsulation techniques appeared to enhance scorodite stability under simulated oxic and anoxic environments by reducing the arsenic release rate up to one order of magnitude.
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Lin, Jianlong 1967. "Effect of texture and microstructure of zircnoium [sic] alloys on their oxidation and oxide texture." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85935.
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Zirconium oxide is a barrier against corrosion. The oxidation behavior of zirconium alloys is believed to be related to the properties of the substrate and the zirconium oxide grown on this substrate. Both monoclinic and tetragonal phases of the oxide grown on Zr-2.5Nb and Zircaloy-4 are strongly textured. The volume fraction of tetragonal phase in zirconium oxide was investigated. The tetragonal phase percentage gradually decreases with an increase of the oxide thickness.The oxidation kinetics of Zr-2.5Nb and Zircaloy-4 was investigated and the results demonstrate that the oxidation rate is related to the volume fraction of tetragonal phase. No texture evolution was observed in both alloys as the oxidation time varied. It was found that the higher the volume fraction of tetragonal phase, the higher oxidation resistance.
The texture formation of the oxide is related to the texture of the substrate. A model of crystal orientation relationship between alpha-Zr and the monoclinic phase was applied to explain the formation of oxide textures on substrates having different textures. Good agreement between the results predicted from the model and the experimental results were obtained. A crystallographic orientation relationship between the monoclinic and tetragonal oxide phases is proposed based on the texture investigation of both phases. Various methods were applied to modify the texture of Zr-2.5Nb. Heat treatment at 560°C caused decomposition of the beta-Zr phase. This heat treatment only slightly increased the sharpness of texture of the alpha-Zr phase and heat treatment improved the oxidation resistance of Zr-2.5Nb. The improvement is attributed to a change of morphology of the beta-Zr phase. High temperature heat treatment at 855°C significantly changes the microstructure and texture of the substrate. A needle shape second phase formed inside the alpha-Zr phase is responsible for the increase of oxidation rate. Cold deformation causes the texture in the Zr-2.5Nb substrate to change from (1120)[1100] to (11 23)[1100]. The change of the texture degrades the oxidation resistance of Zr-2.5Nb.
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Martin, Étienne. "A microtexture characterization of recrystallization and twinning in magnesium." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95140.
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The evolution of texture and microstructure during the deformation of two Mg-based (+Al, Mn, Zn) alloys has been studied under various conditions of temperature and strain rate. The tested materials were taken from AZ31 and AM30 extruded tubes. The mechanism of recrystallization was investigated by using uniaxial compression, while twinning was studied under uniaxial tension testing. Optical metallography, X-ray analysis and EBSD techniques were employed to study the texture and grain scale development. The first part of the investigation focused on the misorientations that apply to the different mechanisms of new grain formation during the hot compression of magnesium alloy AM30. This approach led to the identification of three types of microstructural features produced during deformation at high temperature (350°C at a strain rate of 0.001s-1). In the first, microbands were produced in grain interiors due to the accumulation of basal dislocations. Their orientation changes involve rotations of the basal planes to a more favorable orientation for glide, leading to geometric softening. In the second, two different types of DRX nuclei were observed, i.e. those formed i) by bulging and ii) by continuous dynamic recrystallization. Although visually distinct, the two mechanisms are formed as a result of dislocation-based processes that produce c-axis rotations toward the loading axis. For low misorientation angles, the boundary character is consistent with the accumulation of basal dislocations. Once nuclei of the latter two types have formed, however, only those orientations belonging to the RD-TD fibre are able to grow. In this way, recrystallization leads to the retention of the main characteristics of the initial RD-TD texture. The second part focused on the mechanisms associated with variant selection during contraction and double twinning. These twins are of practical interest since they have a high potential for texture randomization. For this purpose, magnL'évolution des orientations cristallographiques préférentielles et de la microstructure de deux alliages de magnésium, soit AZ31 et AM30, a été étudiée à des températures et à des vitesses de déformation différentes. Les échantillons des deux alliages utilisés ont été prélevés sur des tubes extrudés. Des essais de traction et de compression uniaxiales ont été effectués dans le but de comprendre les mécanismes à l'origine de la formation des macles et des grains recristallisés. L'effet de la recristallisation sur les macles primaires (ou de contraction) et secondaires (ou d'extension) a finalement été étudié. La première partie de l'étude porte sur les relations de désorientation qui sont associées aux joints de grain qui se forment durant la compression de l'alliage de magnésium AM30 à haute température (soit 350 °C, et à une vitesse de déformation de 0.001s-1). Cette méthode de caractérisation a permis l'identification de trois types de composantes structurales. Premièrement, des microbandes se forment au centre des grains par l'accumulation de dislocations basales. Ces bandes produisent des rotations qui positionnent les plans de glissement basal de façon à faciliter le glissement des dislocations. Ainsi, un adoucissement géométrique est généré, ce qui a pour effet de diminuer la contrainte d'écoulement. Deuxièmement, la recristallisation engendre la formation de nouveaux grains aux joints des grains initiaux. Deux mécanismes de recristallisation sont observés : les nouveaux grains sont créés soit par la migration des joints de grain ou par recristallisation continue. Bien que visuellement distincts, ces deux mécanismes sont tout deux initiés par une accumulation de dislocations. Les résultats ont démontré que les nouveaux grains ayant une orientation similaire à celle des grains initiaux sont avantagés au niveau de la croissance. Ainsi, la recristallisation a tendance à retenir les orientations
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Morales, Higa Ken. "Ladle shrouds as flow control devices for tundish operations." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103761.
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The performance characteristics of a tundish, such as the flotation of inclusions and of slag entrainment, are largely influenced by the fluid flow phenomena. Physical and mathematical modeling in water is widely used to understand fluid flows in a tundish, and as a tool to improve, control and design procedures for high quality steel processing operations. These approaches were used to study the performance of fluid flow for a new design of ladle shroud. The new "Dissipative Ladle Shroud" (DLS) was studied, using a one third scale, delta shaped, four-strand tundish. The results were compared with those achieved with the standard ladle shroud. The standard k-ε turbulence model, together with the continuity and momentum equations, were employed in order to analyze, and visualize, the velocity fields generated within the tundish operating at steady state. Different cases have been analyzed, including a conventional ladle shroud (LS) with a bare tundish, and a tundish furnished with an impact pad. Similarly, the new design of the shroud (DLS) was studied under equivalent conditions. The physical experiments included the use of Particle Image Velocimetry (PIV) and conductivity tracer techniques. The PIV measured the instantaneous velocities at the outlet of the DLS and the LS at different flow rates, showing the detailed jetting characteristics of water leaving the two types of ladle shroud. Residence Time Distribution (RTD) curves were also obtained for the different flow arrangements previously mentioned, and the dispersion of a colored dye tracer was observed at different intervals of time during tundish operation, and analyzed using the video visualization technique.Les caractéristiques de performance d'un répartiteur telles la flottaison des inclusions et de la scorie sont largement influencées par les phénomènes d'écoulement des fluides. Les modèles physiques et mathématiques sont communément utilisés pour comprendre la dynamique des fluides dans un répartiteur et pour améliorer, contrôler et concevoir les procédés de traitement d'acier de haute qualité. Cette approche a été utilisée pour étudier la performance de la dynamique des fluides avec un nouveau design de poche de couleé. La nouvelle "Dissipative Ladle Shroud" (DLS) a été étudiée en utilisant une échelle d'un tiers de répartiteur, en forme delta et possédant quatre drains de couleé. Les résultats ont été comparés avec ceux obtenues avec le poche de couleé normal. Le modèle de turbulence k-ε, avec les équations de conservation des masses et de quantité de mouvement, a été utilisé pour analyser et visualiser les champs de vitesse générés par l'opération du répartiteur en conditions stables. Différents cas ont été analysés, incluant un "conventional ladle shroud" (CLS) avec un répartiteur vide, et un répartiteur muni d'un bloc d'impact. De même, le nouveau design de poche de couleé (DLS) a été étudié sous des conditions équivalentes. Les expériences physiques incluent l'utilisation du "Particle Image Velocimetry" (PIV) et de techniques de traceur de conductivité. Le PIV mesure la vitesse instantanée à l'issue du DLS et du CLS à différents taux de flux, en montrant les caractéristiques détaillées du jet d'eau quittant les deux types de poche de couleé. Des courbes de Distribution des Temps de Résidence (RTD) ont également été obtenues pour les différents arrangements de flux précédemment mentionnés, et la dispersion d'un traceur de teinture colorée a été observée et analysé à différent intervalles de temps pendant l'opération du répartiteur en utilisant une vidéo de visualisation technique.
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Uddin, Salah. "Surface charge characterization and flotation of an ultramafic nickel ore." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107688.
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AbstractAbout 300 million tonnes of inferred Ni resource in ultramafic hosted rocks is present in 'Thompson Nickel Belt' in north central Manitoba. The processing challenges result from electrostatic interaction between pentlandite (the main Ni-mineral) and serpentine (the main gangue and one of the MgO minerals). As a contribution to meeting the challenge, the thesis examines the role of particle and bubble surface charge and the effect of fibre disintegration on flotation behavior of an ultramafic Ni ore sample. For surface charge characterization the sedimentation potential technique was used. A novel integrated device was developed to measure sedimentation potential, conductivity and pH simultaneously. Maxwell's model was used to calculate volume fraction of dispersed phase from conductivity, and zeta potential, when appropriate, was calculated from the Smoluchowski equation. The technique was validated by showing good agreement with iso-electric point for alumina, silica and bubble suspensions with electrophoresis measurements. The technique was extended to characterize mixed minerals including ultramafic ore, and bubbles in the presence of particles. The results provided some evidence of metal ion adsorption on particles and the possibility of non-hydrophobic particle attachment to bubbles. The latter was reinforced by visualization studies of a pendant bubble exposed to particle suspensions.A novel fibre disintegration strategy was devised combining both chemical (acid) and physical (grinding) treatment based on work to enhance carbon dioxide uptake by serpentine. Using HCl, subsequent conventional flotation (amyl xanthate, soda ash and MIBC) gave significantly improved results over the untreated ore. Using H2SO4, arguably the practical option led to flotation without collector due to elemental sulphur formation on pentlandite, and without frother due to high ionic strength solutions. Improved Ni grade-recovery with higher MgO mineral rejection was achieved. Structural changes in the fibres were followed using various spectroscopic techniques and a mechanism of fibre disintegration suggested.Environ 300 millions de tonnes de ressources inférées de Ni ultramafiques hébergé est présent dans 'ceinture nickélifère de Thompson' dans le centre-nord du Manitoba. Le traitement des défis résultant de l'interaction électrostatique entre pentlandite (le principal Ni-minéraux) et la serpentine. En tant que contribution à relever le défi, la thèse examine le rôle des particules et la charge de surface des bulles et l'effet de la désintégration des fibres sur le comportement de flottaison d'un échantillon de minerai de nickel ultramafiques. Pour la caractérisation de charge de surface de la technique de sédimentation potentielle a été utilisée. Un nouveau dispositif intégré a été développé pour mesurer le potentiel de sédimentation, la conductivité et le pH simultanément. Le modèle de Maxwell a été utilisée pour calculer la fraction volumique de phase dispersée de la conductivité, et le potentiel zêta, le cas échéant, a été calculée à partir de l'équation de Smoluchowski. La technique a été validée en montrant un bon accord avec l'iso-électrique de point pour les suspensions d'alumine, de silice et de bulles avec des mesures d'électrophorèse. La technique a été étendue afin de caractériser les minéraux mélangés, y compris de minerai ultramafiques, et des bulles dans la présence de particules. Les résultats ont fourni des preuves de ion métallique adsorption sur les particules et la possibilité de l'attachement des particules non-hydrophobe à bulles. Ce dernier a été renforcée par des études de la visualisation d'une bulle Pendentif exposés à des suspensions de particules.Une stratégie nouvelle fibre de désintégration a été conçu combinant à la fois chimique (acide) et physiques (broyage) un traitement basé sur le travail pour améliorer l'absorption du dioxyde de carbone par la serpentine. En utilisant HCl, à la suite de flottation conventionnelle (amyl xanthate, la cendre de soude et de MIBC) a donné des résultats nettement améliorés au cours des minerais non traités. Utiliser H2SO4, sans doute l'option la pratique conduit à de flottaison sans collecteur due à la formation du soufre élémentaire sur la pentlandite, et sans buse due à des solutions à haute force ionique. Amélioration de qualité Ni-reprise avec le rejet supérieur de MgO de a été atteint. Les changements structurels dans les fibres ont été suivis en utilisant diverses techniques de spectroscopie et d'un mécanisme de désintégration de fibre suggéré.
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Ederer, Leslie. "The effect of zinc stearate on the compaction and sintering characteristics of a Ti-6%A1-4%V hydride-dehydride powder /." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=29857.
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Powder metallurgy (P/M) processing has become an important technique replacing many casting applications, especially for the fabrication of refractory metals where very high melting temperatures are required. Improvement in powder production, cleanliness and characterization techniques, combined with an increased understanding of basic compaction and sintering principles and a need for metals with high strength to weight ratios has led to an increased interest in titanium powder utilization. P/M techniques for Ti-6Al-4V powder can enable the production of high quality parts at lower processing temperatures and cost. For most applications prealloyed powder produced by the hydride-dehydride process (HDH) is used, due to the lower cost of this powder as compared to Ti-6Al-4V powder produced by other methods.General characterization of a Ti-6Al-4V HDH powder and the effects of using a zinc stearate on the green and sintered density were examined at different compaction pressures and sintering temperatures. (Abstract shortened by UMI.)
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La-Orchan, Wittaya. "Quantification of the reduced pressure test." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28812.
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The concentration of hydrogen is one of the most important parameters in liquid aluminum processing because it is responsible for gas porosity which affects casing quality, ie. pressure tightness, mechanical properties etc. In order to gain optimum quality, the amount of hydrogen dissolved in liquid aluminum must be known prior to casting. This has led to the development of several techniques to quantify hydrogen in liquid aluminum. Among these is the Reduced Pressure Test (RPT). The RPT is simple, very inexpensive and commonly used in aluminum foundries to obtain a qualitative evaluation of the melt hydrogen level.In this thesis the development of the RPT to a truly quantitative level is discussed. This includes redesigning of the steel mold and the application of a riser. The mold was redesigned to improve the test sensitivity while a CO$ sb2$-bonded sand riser was applied in order to eliminate volumetric shrinkage and ensure a constant volume sample. As the sample has a constant volume, either the sample weight or density can be used to quantify the hydrogen content. The simplest technique is to use the sample weight.
Several parameters that affect the test sensitivity and reproducibility were studied, such as chamber pressure, amount of inclusions, pouring temperature, and mold temperature. It was found that there are two important parameters that strongly affect the test; chamber pressure and amount of inclusions. The lower the chamber pressure the better the test sensitivity but the poorer the test reproducibility. Increasing the amount of inclusions improves the test sensitivity.
The constant volume sample can be used to predict the amount of hydrogen in the melt for various types of alloys including 319, 356, 357 and 413 within a reasonable margin of error. The error as measured by this technique was found to be in the range of $ pm$0.025-0.049 ml./100 g.Al. if the sample weight is used, and in the range of $ pm$0.025-0.047 ml./100 g,Al. if the sample density is used.
A simple mathematical model based on a mass balance approach was developed to calculate pore size and sample density. The model predicts the density accurately for various types of alloys and different melt treatments.
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Meratian, Isfahani Mahmood. "Thermal analysis of aluminum foundry alloys by a novel heat pipe probe." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28846.
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A new application of heat pipes is introduced. The present research deals with the development of a heat pipe for the on-line quality control of liquid aluminum silicon foundry alloys.Thermal analysis is a technique whereby a small quantity of a melt is allowed to solidify while its cooling curve is recorded. Analysis of the cooling curve with standard mathematical algorithms allows one to determine a number of useful parameters that characterize the liquid and solid states of the material. In aluminum-silicon casting alloys thermal analysis is often used to assess the grain size and degree of eutectic modification of the alloy before pouring.
A novel probe has been developed for conducting thermal analysis of aluminum alloy melts. The probe, which resides in the melt, need not be withdrawn as it solidifies a small sample (i.e. button) at a predetermined cooling rate. Once the cooling curve results have been acquired, the probe can be instructed to remelt the frozen button and await instructions for analyzing a fresh sample.
The operating principle of this novel device is based on heat pipe technology. In simple terms, a heat pipe consists of a condenser and an evaporator which contain a relatively small quantity of working substance fluid. As heat is absorbed by the evaporator, the liquid phase of the working substance is vaporized and subsequently condensed on the condenser walls from which heat is extracted.
It has been shown that the designed probe, which is classified as a gas loaded annular thermosyphon, is completely workable in the range of conditions typically encountered in the thermal analysis of aluminum alloys. The thermal analysis results obtained with this new technique are in a good agreement with those of conventional thermal analysis. In addition, the new method is applicable to a wider range of operating conditions and is easier to use. Based on the semi-continuous nature of the new method, it does not need pre-preparation (materials, labour, pre-heating, thermocouple installation for each test, isolation of the sampling cup, etc.) to start thermal analysis. Also, from a cooling rate point of view, the system is well controllable. Moreover, it is shown that the probe is simple in construction, easy to use, and intelligent enough to provide semi-continuous thermal analysis. There are no consumable materials and moving parts.
Thermal analysis results are reported for pure aluminum, hypoeutectic aluminum silicon (356) and eutectic aluminum silicon (413) casting alloys. Agreement in the results between the new and conventional systems is shown to be excellent. Finally, a heat transfer/solidification model of the heat pipe thermal analysis probe is derived and validated.
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Tian, Chenguo. "Filtration of liquid aluminum with reticulated ceramic filters." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28932.
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Fluid flow and filtration phenomena associated with filtration of liquid aluminum using reticulated ceramic filters were systematically investigated. It was found that fluid flow through this type of filter could be described by Darcy's Law up to a Reynolds number of 8, and the permeability of this type of filter ranged from about $9 times10 sp{-3}$ to $4 times10 sp{-2} rm mm sp2$.Parameters affecting filtration processes during the initial period were identified, some of which could be quantified numerically using a 2-D computational domain. According to these numerical analyses, the clean filter coefficient for this type of filter was linearly dependent on the dimensionless Stokes velocity of the suspended particles, had a $-$0.96 power dependence on the Peclet number, a $-$6.93 power dependence on the effective porosity of the filter, and exhibited only a weak dependence on the Reynolds number, in the Darcy velocity regime.
The dynamic behaviour of this type of filter was analyzed theoretically and simulated numerically using newly proposed correlations relating the filter coefficient and the pressure drop to the amount of particles captured within the filter (the specific deposit), and a model describing the morphology of captured particles. The simulated results showed that the filtration efficiency and the pressure drop increased with inlet particle concentration and filtration time; these increases were however, insignificant when the inlet particle concentration was less than 1 ppm for filtration periods of two hours, however, when the inlet concentration (initial and continued) reached 10 ppm, the change became appreciable.
Experimental data, obtained from liquid aluminum filtration tests conducted by the author in both laboratory and industrial settings, compared favourably with the numerical results.
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D'Souza, Neil S. "Thermal remediation of stainless steel electric arc furnace (EAF) dust." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30239.
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Along with the essential importance of the metallurgical sector, one must recognise that it is also one of the largest sources of environmental pollution. In particular, the problem of electric arc furnace (EAF) dusts is of a growing concern due to the increase in popularity of EAF steelmaking. This dust is classified as a hazardous product due to the elevated content of toxic metals (e.g., Cr).Studies on the properties of EAF dusts are sparse. Experiments were performed in order to determine the chemical and physical characteristics of the dust. It was determined that EAF dust is constituted of randomly distributed agglomerations of homogeneously nucleated particles and entrained particles. The main elements present within the particular dust were iron and chromium, the latter due to the fact that the dust used was formed within a stainless steel mini-mill. The main phases present within the dust were Fe2O3/Fe 3O4 and Cr2O3.
Thermal remediation experiments were then carried out in a computer controlled thermogravimetric system. The parameters studied during the tests included temperature, residence time and heating rate. In addition, the behaviour of the EAF dust during remediation was studied; in terms of weight and volume loss, gas evolution, particle morphology and resulting leachability of the treated product. Furthermore, it was observed that at temperatures greater than 1200°C metal leachability decreased significantly due to a decrease in toxic metal concentration within the treated product and the formation of a resistant, dense, plate-like morphology. At 1600°C, no toxic metals leached out of the remediated EAF dust and volume reduction was significant, resulting in a product that would be safe and more economical to landfill.
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Purcell, Anne 1960. "Mathematical modelling of temperature evolution in the hot rolling of steel." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=30269.
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The CANMET-McGill Mathematical Model has been expanded and improved to provide a more comprehensive predictive tool for simulation of temperature evolution in the hot rolling of steel. The model uses a Windows(TM)-based, user-friendly, graphical interface and the explicit finite-difference method in two dimensions to simulate the rolling of flat product.Data input options were expanded to allow an initial temperature gradient in the steel to be rolled, the inclusion of a runout table in the calculations, specific chemical compositions and a choice of emissivity values.
A novel, chemistry-dependent thermal conductivity term was developed to account for the variation in heat conduction through the thickness of the steel and to ensure that the temperature of the entire cross-section is accurately predicted. In addition, the model now calculates a heat of transformation for phase changes from austenite to ferrite, pearlite and bainite.
An automated self-calibration module was included to facilitate the calibration of the model's predictions to empirically obtained temperature setpoints.
The model's temperature predictions were validated against both industrial and laboratory data with excellent results.
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Dong, Jin Xiang 1961. "Effect of silicon on the kinetics of Nb(C,N) precipitation during the hot working of steels." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31048.
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The effect of Si on the kinetics of Nb(C,N) precipitation was investigated by using fractional softening measurements. Compression specimens, with diameters of 7.6 mm and lengths of 11.4 mm, were prepared from four Nb microalloyed steels containing a range of Si concentrations from 0.01 wt% to 0.41 wt%. The stress relaxation method was used in the beginning of this work, but the majority of the experimental results were derived from double-hit compression tests, with a strain of 0.3 applied to represent each pass at a strain rate of 0.1/sec. A solution heat treatment was applied immediately prior to each test.It was found that the rate of Nb(C,N) precipitation in hot deformed austenite increases with Si concentration. This phenomenon is attributed to the increases in both the Nb diffusivity and the activities of C and N that result from Si addition. Based on the Dutta and Sellars model, an expression for the effect of strain rate on the precipitation start time has been proposed. The present experimental results can then be extrapolated to mill conditions.
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Ashrafizadeh, Seyed Nezameddin. "Solvent extraction and liquid membrane separation of rhodium." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37698.
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The aim of this work was to develop a viable solvent-extraction based system for the separation of rhodium (Rh) from aqueous chloride solutions. Ultimately, two different systems were developed. Kelex 100, a commercially available derivative of 8-hydroxyquinoline, was used as the extractant reagent in both of these systems. One of the systems involved the supported liquid membrane (SLM) extraction of Rh. In this system a very thin microporous "Gore-Tex" polymer sheet, impregnated with an organic solution of Kelex 100, served as the SLM. The other system involved the conversion of the chlorocomplexes of Rh to bromocomplexes prior to their solvent extraction with Kelex 100.The results of the lab-scale experiments using a SLM of Kelex 100 having a surface area of 44 cm2 are reported. The optimum conditions for Rh permeation were found as a feed solution of 2.5 M HCl and a strip solution of 0.1 M HCl. The SLM was quite stable at the optimum conditions with no sign of organic loss or membrane deterioration after 72 hours of operation. It was determined that the HCl activity gradient across the membrane acts as the driving force that "pumps" the non-aquated Rh chlorocomplexes against their concentration gradient. The mechanism of Rh permeation was the ion-pair formation between the protonated Kelex 100 and RhCl6 3- complexes. The rate of Rh permeation was in the order of 10-6 mol.m-2.s-1. The mechanism of HCl and H2O permeation, which were co-extracted along with Rh chlorocomplexes, were found to be the hydration of protons at the low feed acid region and the formation of microemulsions at the high feed acid region. The permeated acid and water were separated from the SLM receiving phase by contacting the latter phase with an organic solution of trioctylamine (TOA). The chlorocomplexes of Rh(III) and acid are readily extracted to the TOA organic phase and subsequently subjected to differential stripping with a concentrated solution of Cl- and a mild NaOH solution, respectively. By interfacing the TOA solvent extraction with the SLM of Kelex 100 highly concentrated solutions of Rh (at least 10 times the initial concentration) and raffinates essentially free of rhodium were produced.
The UV-Visible investigations revealed that the bromocomplexes of Rh undergo aquation to a much lesser extent than that of the chlorocomplexes. The chlorocomplexes of Rh were converted to bromocomplexes by precipitating first the Na(NH4)2Rh(NO2)6 salt and subsequently dissolving that in an HBr solution. The newly formed bromocomplexes of Rh(III) responded very favorably to extraction with Kelex 100. Relatively high distribution coefficients, about 20, and very steep extraction isotherms were generated. The freshly loaded Kelex 100 organic was efficiently stripped upon contact with a strip solution of 6--8 M HCl and a contact time of 10--12 hours. The developed system shows high promise from a practical implementation point of view.
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Külünk, Bahadir. "Kinetics of removal of calcium and sodium by chlorination from aluminum and aluminum-1wt% magnesium alloys." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39752.
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The kinetics of calcium and sodium removal at 730$ sp circ$C by chlorination from commercial purity (99.7% Al) and aluminum-1wt% magnesium alloys has been investigated. The contribution of chlorine containing gas bubbles, of intermediate reaction products generated by the chlorination process, as well as evaporation through the melt surface, to the removal of calcium and/or sodium has been documented quantitatively. Experimental parameters investigated were chlorine concentration in the gas bubbles and gas flow rate. The measurement of frequency of bubble formation at the tip of the gas bubbling nozzle enabled the surface areas of the bubbles to be estimated which in turn enabled melt phase mass transfer coefficients for the bubbles to be calculated.It was demonstrated that the removal of calcium and sodium followed first order reaction kinetics with respect to calcium and sodium concentrations. The removal of the above mentioned elements was represented well by a kinetic model in which mass transfer of sodium and calcium in melt phase was rate limiting.
In the case of the magnesium containing alloys, the MgCl$ sb2$ salt phase that was generated during chlorination was found to have a profound effect on the removal of calcium and sodium. The contribution of the salt phase to the removal of these elements was calculated to reach as high as 60%. In commercial purity aluminum, however, while the major contribution to the removal of calcium was from the chlorine containing gas bubbles, the major contribution to the removal of sodium was calculated to be evaporation of sodium through the melt surface.
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Zhang, Qingsong 1963. "Sphalerite activation in the presence of iron ions." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41802.
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Flotation of sphalerite with xanthate in the presence of iron ions has been studied as a function of pH. Sphalerite floated readily at pH 8-11 in the presence of ferrous ions, but not in the presence of ferric ions. The Fe$ sp{2+}$ ion concentration, pH and oxygen concentration were shown to be factors in controlling flotation. Electrokinetic measurements indicated that the surface charge increased in the presence of Fe$ sp{2+}$ ions and oxygen, and decreased upon adding xanthate and in the presence of Fe$ sp{2+}$ ions with the absence of oxygen.As a prelude to surface analysis to try to identify the species responsible for the sphalerite flotation, bulk precipitates formed from iron salt and xanthate solutions under various conditions were obtained and analysed. Analysis techniques included ultraviolet spectroscopy, infrared spectroscopy, x-ray diffraction and Mossbauer spectroscopy.
It was tentatively concluded that the bulk precipitates contained three ferric components: two hydroxy xanthates, Fe(OH)$ sb2$X and Fe(OH)X$ sb2$ and an iron oxide, FeO$ sb{ rm x}.$
Iron xanthate precipitates prepared over the pH range 6-12 showed a flotation response and electrokinetic behaviour similar to those of Fe$ sp{2+}$/xanthate-treated sphalerite.
An ex situ X-ray photoelectron spectroscopic (XPS), ex situ infrared (DRIFTS) and in situ infrared (ATR) investigation of the interaction of sphalerite with ferrous, ferric and xanthate ions at pH 10 was undertaken. The formation of the hydrophobic surface species was found to involve initial adsorption of Fe$ sp{2+},$ followed by oxidation to Fe$ sp{3+}$ and subsequent reaction with xanthate. There was no significant incorporation of Fe$ sp{3+}.$
A three-step reaction mechanism is proposed to account for Fe$ sp{2+}$ ion activation of sphalerite: (i) adsorption of Fe(OH)$ sp+,$ (ii) oxidation to Fe(OH)$ sp{2+}$ on the surface, (iii) reaction with xanthate to form Fe(OH)$ sb2$X or Fe(OH)X$ sb2.$
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Sugondo. "Textures versus microstructure in determining mechanical properties in wires." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59232.
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The aim of this work is to offer a quantitative assessment as to what extent the texture and the microstructure influence the cold headability of steel wires.For this, a set of cold drawn low carbon steel wires/AISI 1030 were prepared. The samples were drawn, without heat treatment, in between passes of up to 78% reduction in area (RA) in 5 passes. The deformed samples were then heat treated according to various schedules.
Texture development was studied at a given thickness, by measuring the (110), (200) and (211) pole figures by X-ray diffraction; furthermore, the results were represented and using the Orientation Distribution Function (ODF). A strong $ langle$110$ rangle$ texture was found.
Using special dies, compression tests were made in order to obtain information on such mechanical properties as the yield strength and the homogeneous strain energy.
Multiple regression analysis was made in order to correlate the aspect ratio, the grain size, the Taylor factor and the maximum ODF intensity against the yield strength and the homogeneous strain energy.
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Charbonnier, A. (Alain). "Secondary dendrite ARM spacing determination in Al-Si casting alloys by conductivity measurements." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60694.
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Al-Si-Mg alloys containing 7% silicon are the most widely used aluminum foundry alloys owing to their good mechanical properties and excellent castability. Nevertheless, design engineers traditionally apply a design casting factor when designing cast components to ensure that proper strength will be obtained in spite of the recent emergence of techniques of control of the molten alloy quality on which depend, afterwards, the mechanical properties of the castings.In this study, the feasibility of using electrical conductivity to non-destructively predict secondary dendrite arm spacing was investigated on both as-cast and heat treated alloys. In the as-cast condition, conductivity decreases linearly with increasing DAS from 30 $ mu$m, while, below 30 $ mu$m, conductivity readings are influenced by alloying elements retained in solid solution due to the fast solid state cooling rates. Conductivity changes with DAS are more important when the silicon morphology is finer i.e. the alloy modified. After heat treatment, the DAS-conductivity relationships become linear as a result of the homogenisation of the aluminum matrix, but the slopes of the lines are small and the accuracy of DAS determination does not extend below 15 $ mu$m. Conductivity is also greatly influenced by the degree of precipitation achieved during artificial aging so that the determination of DAS by conductivity measurement is best used after quenching (T4 condition).