Дисертації з теми "Metals at high temperature"
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1
Rauch, Nicole. "High temperature spreading kinetics of metals." [S.l. : s.n.], 2005. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-25946.
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2
Munro, Keith Alistair. "High-pressure high-temperature behaviour of the lanthanide metals." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28881.
Повний текст джерелаАнотація:
The high-pressure behaviour of the lanthanide series of metals has been the subject of study since the work of Percy Bridgman in the 1940s. Differences in said behaviour between the different lanthanide metals are attributed to the increasing occupation of the 4f electron shell as Z increases. Upon compression, or as Z decreases, the trivalent lanthanides (La to Lu, excluding Eu and Yb) undergo a common phase transformation sequence through various close packed structures: hcp → Sm-type (the structure adopted by samarium at ambient conditions) → dhcp → fcc → distorted fcc (d-fcc). Upon further compression, the lanthanide metals experience a first order transition to a "volume collapsed" phase. Many studies have focused on the low-Z members of the series, since the various phase transitions occur at much lower pressure where it is comparatively easy to collect high quality data. By contrast, the other members of the series have received comparability little attention, and there are even fewer reports of the structural behaviour of the lanthanide metals at high pressure and high temperature. This thesis contains the results of angle-dispersive x-ray powder diffraction experiments at high pressure and high temperature of the various members of the lanthanide metals. Ce has been the subject of many previous studies, but a systematic x-ray diffraction study of the fcc/d-fcc phase boundary has never been attempted. Furthermore, the location in P-T space of the high temperature fcc/bct/d-fcc triple point has only been inferred, due to the lack of data on the fcc/bct phase boundary at high temperature. The high-pressure high-temperature phase diagram of Ce is presented and discussed. La is unique amongst the lanthanide metals due to its empty 4f shell at ambient conditions. Despite this, La undergoes the common lanthanide transformation sequence up to the d-fcc phase, after which it undergoes a re-entrant transition back to the fcc phase at 60 GPa. The diffraction peaks of d-fcc La are shown in this thesis to undergo changes in intensity upon compression, indicating a transformation to the oI 16 structure found in Pr. La is one of the few elements whose behaviour has been unknown above 100 GPa, and results of La's structural behaviour upon compression to 280 GPa are presented and discussed. At 76 GPa, La begins a transition from the fcc phase to a new phase with the bct structure. Finally, the d-fcc→fcc re-entrant phase transition has been determined at various temperatures, and the d-fcc stability region has been mapped out. Finally, x-ray diffraction experiments were performed on Gd up to 100 GPa and ~700 K, to determine the structure of the d-fcc phase and the "volume collapsed" phase. While d-fcc Gd does not undergo pressure-induced changes similar to its low Z brethren, the d-fcc Gd remains stable up to 41 GPa at 700 K, putting a constraint on the d-fcc stability region. The data collected on Gd's "volume collapsed" phase cannot be fitted to the currently accepted mC4 structure. This has implications for our understanding of the lanthanide series as a whole, since most of of the heavier members, and some of the lighter lanthanides, are reported to adopt the mC4 structure.
3
Hudson, David Mark. "The high temperature evaporative refining of metals." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330210.
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4
Mirmasoudi, Sara. "High Temperature Transient Creep Analysis of Metals." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1452693927.
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5
Romans, Edward John. "Interfaces between normal metals and high temperature superconductors." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389892.
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6
Bacroix, Brigitte. "Prediction of high temperature deformation textures in FCC metals." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74036.
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7
Moricca, Maria del Pilar. "High temperature oxidation characteristics of Nb-10W-XCr alloys." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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8
Cain, Victoria. "High temperature creep behaviour niobium bearing ferritic stainless steels." Thesis, Cape Peninsula University of Technology, 2005. http://hdl.handle.net/20.500.11838/1249.
Повний текст джерелаАнотація:
A thesis submitted to the Faculty of Engineering in
fulfilment of the requirements for the degree of Master of
Technology in Mechanical Engineering
2005The objective of this project was to monitor the high temperature creep behaviour of 441 stainless steel. Two different alloys of 441 were investigated; the main difference between them being the Niobium content. Particularly imporlant to the project was how the Niobium content and grain size affected the creep resistance of the material. Creep tests were performed using purpose built constant load creep test rigs. Initially the rigs were not suitable for the testing procedures pertaining to this project. This was due to persistent problems being experienced with regards the reliability and reproducibility of the rigs. After various modifications were made the results produced from the rigs were consistent. Creep test data was used in order to determine the mechanism of creep that is operative within the material (at a predetermined temperature) under a predetermined load. Particular attention was paid to the resulting stress exponents. in order to identify the operative creep mechanism. The identification of the operative creep mechanisms was also aided by microscopical analysis. This analysis was also necessary to monitor how the grain size had altered at various annealing temperatures. Heat treatment was used as a method to alter the high temperature strength and microstructure of the material. Heat treatments were performed at various temperatures in order to determine the ideal temperature to promote optimum creep resistance of 441. All heat treatments were performed in a purpose designed and built high temperature salt bath furnace. The commissioning of the salt bath formed part of the objectives for this project. Sag testing was also conducted, using purpose built sag test rigs. It was necessary to design and manufacture a sag test rig that could be comparable to the industry accepted method of sag testing known as the two-point beam method, as this method is believed to produce inconsistent results. Conclusions have been drawn from the results of the data and from previous research on the subject matter.
9
Ma, JunKun. "Synthesis of dense TiC-Ti based cerments via self-propagating high temperature synthesis and quasi-isostatic pressing /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2004. http://wwwlib.umi.com/cr/ucsd/fullcit?p3148261.
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10
Prescott, Robert. "The corrosion of alloys and metals in high-temperature chlorine-bearing gases." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236260.
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11
Tyreman, C. J. "The high temperature corrosion of metals and alloys in HF-containing environments." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358527.
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12
Joumaa, Hady K. "Development of a uniform-droplet spray apparatus for high melting temperature metals." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32352.
Повний текст джерелаАнотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Leaf 230 blank.
Includes bibliographical references (leaves 157-158).
The building and operation of a high-temperature uniform droplet spraying (UDS) apparatus extend the performance and capabilities of powder based manufacturing processes. Although the main concepts of operation of the high-temperature apparatus are typical to the ones currently existing in the Droplet Based Manufacturing (DBM) laboratory, they are implemented with some different systems whose capabilities satisfy the process needs for solder alloys. The motivation of this research is to design, test, optimize, and assemble the new UDS apparatus systems aiming to produce the powder of high melting temperature metal, mainly copper. At first, the limited capabilities of the current apparatuses are revealed and the characteristics of the high-temperature apparatus are presented. A new design concept is set according to these characteristics. The UDS apparatus is then described in detail with emphasis on the newly installed systems that give the apparatus its desirable features. After that, the assembly processes of all the systems are explained. The next step is the testing process of the systems that analyzes and optimizes their performance. At the end, the experimental outcome of this research is presented. In conclusion, partial success in spraying 300 to 700[mu]m copper droplets is achieved. These results are evaluated and their influencing factors are discussed. Further improvements in orifice mounting and prevention of degassing from the crucible and insulation need to be considered for consistent success.
by Hady K. Joumaa.
S.M.
13
Taylor, Mark J. D. "Processing of porous high melting temperature metals using a removable second phase." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18216/.
Повний текст джерелаАнотація:
The production of high melting temperature porous metals using a removable second phase has been conducted using two different methods with two different categories of second phase. The first of these is the production of a porous high temperature metal using a nickel copper alloy which has undergone solidification-induced phase separation, followed by phase removal. In this system, the removable phase is an intrinsic part of the alloy (formed as part of the microstructure during solidification) which has been removed using a ferric chloride solution. The alloy has been processed using three different solidification regimes which have in turn resulted in the production of three distinct porous structures, and pore sizes. For comparison with this method (offering different capabilities for pore and sample size, and scale up), the replication process has also been used, in which the removable phase is a secondary material extrinsic to the alloy. Significant modifications to standard processes were needed to overcome the challenges of high melting temperature metals in order for porous samples from titanium alloy (Ti-811) to be produced. An iterative experimental approach to development of replication processing has been trialled. The procedures used comprised three methods for alloy melting and two methods for applying the required infiltration pressure. The porous metal produced using this method has shown that replication casting is a possible manufacturing route, but significant hurdles are still present before a large scale porous component can be produced and tested.
14
Abdallah, Zakaria. "Creep lifing methods for components under high temperature creep." Thesis, Swansea University, 2010. https://cronfa.swan.ac.uk/Record/cronfa43065.
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15
Cretegny, Laurent. "Fracture toughness behavior of weldments at elevated temperature." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19957.
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16
Pan, Yi. "Formation of Superhexagonal Chromium Hydride by Exposure of Chromium Thin Film to High Temperature, High Pressure Hydrogen in a Ballistic Compressor." PDXScholar, 1991. https://pdxscholar.library.pdx.edu/open_access_etds/1243.
Повний текст джерелаАнотація:
The interaction of hydrogen with metals has great environmental significance in problems ranging from the catastrophic failure of materials due to hydrogen embrittlement to safe and efficient storage of hydrogen as a metal hydride. Chromium (Cr) is widely used as an alloying agent to produce materials such as stainless steel and as an electroplated coating on materials to prevent corrosion and to minimize wear. Hydrogen which co-deposits with chromium during electroplating forms hexagonal close packed CrH or face centered cubic CrH2 which cracks the deposit. The behavior of hydrogen in Cr, especially the crystal structure modifications of metal Cr when it is exposed to hot, dense hydrogen gas is not completely understood. In equilibrium study, chromium hydride has been found of hexagonal close packed structure under 400 °C with high hydrogen pressure. Experiments at higher temperatures are limited by the equipment and technology. This dissertation describes a novel, non-equilibrium method which was used to synthesize a new chromium hydride phase. Single crystal, body centered cubic Cr thin films were prepared by vacuum evaporation. These films were exposed to high temperature (close to the melting point of Cr), high pressure hydrogen gas in a ballistic compressor. This was followed by rapid cooling (>105 ˚C/s) to room temperature. Using the transmission electron microscope (TEM), second phase particles of superhexagonal structure, which has lattice constant A=4.77Å and C/A=1.84, are found in the films. This structure has a volume per Cr atom slightly larger than that of hexagonal closed packed CrH, so that the superhexagonal structure may contain more hydrogen than the hexagonal close packed CrH. The superhexagonal particles have a definite orientation relationship with the matrix: [021][subscript sh] II [OOl][subscript b] and (212)[subscript sh] II (IIO)[subscript ]b. The superhexagonal structure is quite stable in air and at room temperature, but decomposes to body centered cubic Cr when heated by the electron beam illumination in the TEM. No such particles were observed in Cr films exposed to pure argon under similar conditions in the ballistic compressor. Positive identification of hydrogen content was obtained by high-temperature vacuum extraction in a discharge tube. After vacuum extraction, hydrogen spectrum was observed, and the intensity of electron diffraction from superhexagonal structure decreased. Using an energy dispersive spectrometer with the capability of detecting elements down to atomic number six (carbon), no changes in composition of the films were found by comparing the characteristic x-ray spectra of the same film before and after exposure to hot, dense hydrogen in the ballistic compressor. This result suggests that this non-equilibrium method may be used for other metal-hydrogen systems to obtain new structural phases that are of scientific or technological interest.
17
Kakarlapudi, Purushotham Raju. "High temperature oxidation response of Nb-20W-10Cr alloy in air." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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18
Lass, Nils [Verfasser], and Roland [Akademischer Betreuer] Zengerle. "Pneumatically actuated high temperature resistant printhead for molten metals based on the StarJet principle." Freiburg : Universität, 2016. http://d-nb.info/1122831838/34.
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19
Rangavittal, Bharath Vasudev. "Optimization of Rare Earth Metals (REM) addition in high temperature stainless steel grade 253MA." Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-257206.
Повний текст джерелаАнотація:
The focus of this thesis work is to optimize rare earth metal (REM) addition in Therma 253MA, an austenitic stainless-steel grade in order to get a good trade-off between oxidation resistance property and the amount of big REM inclusions formed. Big REM inclusions are detrimental to material properties and REM is required to be dissolved in the matrix for improving the oxidation resistance. REM optimization can also lead to economical savings for Outokumpu. The distribution of REM between matrix and inclusion is affected by factors such as REM addition, initial oxygen and sulphur contents and time to casting of the melt. The re-oxidation of melt in the tundish also affects the REM distribution. Hence, the effect of these factors on the inclusion characteristics is investigated by analysing samples with different REM additions, using light optical microscope (LOM) and scanning electron microscope (SEM). LOM analysis focussed on stringer inclusion characteristics. SEM+EDS analysis is done using automated "INCA Feature" software with focus on overall inclusion characteristics. Oxidation and creep tests are also performed to study the effect of different REM additions on oxidation and creep behaviour. The results from inclusion analysis show that increasing REM addition and time to casting has a bad effect on stringer and overall inclusion characteristics. The re-oxidation in the tundish influences the inclusion formation, but does not affect the stringer characteristics. The resistance to oxidation of the samples is also compared and is observed to increase within increasing REM addition. Finally, this works suggests an optimal REM addition for Therma 253MA to get a good balance between oxidation resistance and amount of big inclusions.Fokus för detta avhandlingsarbete är att optimera tillsats av sällsynt jordartsmetall (REM) i Therma 253MA, en austenitisk rostfritt stålkvalitet för att få en bra avvägning mellan oxidationsbeständighetsegenskap och mängden stora REM-inneslutningar som bildas. Stora REM-inneslutningar är skadliga för materialegenskaperna och REM måste lösas i matrisen för att förbättra oxidationsbeständigheten. REM-optimering kan också leda till ekonomiska besparingar för Outokumpu. Fördelningen av REM mellan matris och inkludering påverkas av faktorer såsom REM-tillsats, initialt syre- och svavelinnehåll och tid till gjutning av smältan. Re-oxidation av smälta i tunden påverkar också REM-fördelningen. Följaktligen undersöks effekten av dessa faktorer på inkluderingsegenskaperna genom att analysera prover med olika REM-tillsatser, med användning av ljusoptiskt mikroskop (LOM) och avsökning av elektronmikroskop (SEM). LOM-analys fokuserade på stringer-inkluderingsegenskaper. SEM + EDS-analys görs med hjälp av automatiserad "INCA Feature" -programvara med fokus på övergripande inkluderingsegenskaper. Oxidations- och krypningstest utförs också för att studera effekten av olika REM-tillsatser på oxidation och krypbeteende. Resultaten från inkluderingsanalys visar att ökande REM-tillsats och tid till gjutning har en dålig effekt på stringer och totala inkluderingsegenskaper. Återoxidationen i tunden påverkar inkluderingsbildningen, men påverkar inte stringeregenskaperna. Motståndet mot oxidation av proverna jämförs också och observeras öka inom ökande REM-tillsats. Slutligen föreslår detta ett optimalt REM-tillägg för Therma 253MA för att få en bra balans mellan oxidationsmotstånd och mängd stora inneslutningar.
20
Ritwik. "Measuring the viscous flow behaviour of molten metals under shear." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/6686.
Повний текст джерелаАнотація:
The flow behaviour of liquid metals (Sn, Pb and Sn-Pb eutectic) under different shearing conditions is investigated. Experiments were performed with two designs of concentric cylinder viscometers: rotating the inner cylinder (Searle) and rotating the outer cylinder (Couette). The latter technique is uncommon and the equipment was optimised with standard oils. The flow behaviour for the metals differs in the two systems. The curves of 'apparent' viscosity versus shear rate may be divided into two regimes: I. At lower shear rates (<200 s-1): a reduction of 'apparent' viscosity with shear was observed with both viscometers. It is suggested that the high density and high surface tension of the metals and eccentricity between the cylinders at low shear rates, leads to instabilities. Results at low shear rates were therefore discarded and further detailed analysis would be required for a fuller understanding of this behaviour. II. At higher shear rates: a steady, shear-independent behaviour of 'apparent' viscosity with shear rate is observed in the Couette system (upto 600 s-1) whereas in the Searle system the 'apparent' viscosity increases with shear rate (upto 2600 s-1). From hydrodynamic theory about Newtonian fluids, it is suggested that in the Searle type viscometer, the fluid is unstable and Taylor vortices are expected at low shear rates (~80 s-1). This gives rise to an increase in the 'apparent' viscosity with shear rate. Whereas, in the Couette type, the flow is more stable, resulting in a steady 'apparent' viscosity. This interpretation is consistent with liquid metals behaving as Newtonian fluids, but further research is required to confirm this. The author suggests further experiments, with the prime one being the investigation of the fluid with counter and co-rotation of the cylinders in order to observe more complex flows. The results are expected to have implications in the modelling of flow for liquid metal processes, especially the initiation of Taylor vortices under the unstable flow conditions produced by rotating the inner cylinder.
21
Huang, Yi. "Mechanical property, microstructural development and constitutive analysis associated with the high temperature deformation of Inconel 718." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368453.
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22
Knott, Ryan Christopher. "High temperature durability of metals for use in a particle heating receiver for concentrated solar power." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53117.
Повний текст джерелаАнотація:
An experimental investigation is presented on a novel High Temperature Falling Particle Receiver for Concentrated Solar Power (CSP) to quantify the extent of erosion of the receiver structural materials by the flowing particulate matter. The current receiver design uses a series of metal wire mesh screens to slow down the particulate flow through the receiver in order to increase their residence time thereby achieving the desired temperature rise within the receiver without the need for particulate recirculation. The solid particulates are gravity fed through the receiver where they absorb the incident thermal energy before flowing to a high temperature storage bin upstream of a heat exchanger where the heat stored in the particulate material is transferred to the working fluid for the power cycle. To assess the effective life of the receiver, this experimental investigation is undertaken. This thesis includes the development of an apparatus to test wire meshes under high temperature and particle abrasion conditions, and the presentation and analysis of these results.
23
Briggs, R. J. "In situ study of polymorphism and melting of metals and compounds under extreme conditions of high pressure and high temperature." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1389060/.
Повний текст джерелаАнотація:
This thesis presents the experimental investigation of structure and melting of three important materials under extreme conditions of high pressure and high temperature. The melting points of elements and compounds are of fundamental importance for the study of planetary interiors and for fundamental and applied physics. The high pressure apparatus used in this thesis is the diamond anvil cell, which has been used to reach pressures of up to 137 GPa and temperatures up to 6000-7000 K via laser-heating techniques. The melting point has been determined at high pressure by the first onset of liquid scattering in X-ray diffraction patterns that are collected in situ. At temperatures towards the melting point, important information on the crystalline state of these materials has been extracted. The polymorphism of Sn has been studied into the megabar range (P > 100 GPa) at room temperature. The equation of state of Sn has been determined up to 137 GPa. A previously unreported structural transformation occurs at 32 GPa into a body centered orthorhombic structure (spacegroup Immm). Coexistence of this polymorph with a body centered cubic structure (spacegroup: Im-3m) is observed over a wide pressure range. These new findings for this important element are reported within. The melting relations of Sn have been determined to beyond 1 megabar in pressure and reveal a dip in the melt slope followed by a sudden sharp rise between 40 and 70 GPa. High temperature experiments using resistive-heating and laser-heating in the diamond anvil cell reveal the observation of multiple X-ray diffraction signatures at high temperatures. The results are discussed and overlap with the discoveries from the room temperature investigation of Sn. TaC and MgO are two important refractory materials and have also been investigated using laser-heated diamond anvil cell techniques combined with in situ synchrotron X-ray diffraction. TaC has the highest ambient melting temperature of any binary compound. MgO constitutes approximately 37 % of the Earth’s lower mantle and the melting temperature as a function of pressure can provide us with information on the melting behaviour, phase relations and rheology of the Earth’s lower mantle. The results and their impact on current high pressure research are discussed.
24
Rauch, Nicole [Verfasser]. "High-temperature spreading kinetics of metals / Max-Planck-Institut für Metallforschung, Stuttgart. Vorgelegt von Nicole Rauch." Stuttgart : Max-Planck-Inst. für Metallforschung, 2006. http://d-nb.info/980297591/34.
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25
Smith, J. J. "Microstructural characterisation of duplex 316 weld metals : The effects on the mechanical and high temperature properties." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384218.
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26
Bellina, Paul J. "High-temperature oxidation of bulk RuAl alloy." Stuttgart Max-Planck-Inst. für Metallforschung, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?idn=980343135.
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27
Ammer, Khan Ammer Khan. "Metal to ceramic joining for high temperature applications." Thesis, Brunel University, 2003. http://bura.brunel.ac.uk/handle/2438/5375.
Повний текст джерелаАнотація:
The phenomenal growth rate for the use of engineering ceramics is attributed to successful scientific responses to industrial demand. These materials are replacing metal and its alloys in diverse applications from cutting tools and heat engine components to integrated circuits. Joining technology plays a vital role in this changing and evolving technology as success and failure comes with breaking new barriers. It is important to improve existing techniques and to develop new techniques that reliably join simple shape components to form complex assemblies or join dissimilar materials such as metal to ceramic. Joining of ceramics is not simple due to their high chemical stability and low coefficient of thermal expansion (CTE). Joining between metal and ceramic is usually carried out at elevated temperatures and upon cooling thermal residual stresses are induced that lead to joint failure or poor strength. Most metal-ceramic joints cannot be used over 500°C primarily due to the low melting temperature of the interlayer. This investigation was concerned with the successful joining for higher temperature applications (above 500°C) of two dissimilar high temperature oxidation and corrosion resistant materials, Fecralloy and silicon nitride. The primary focus was on the effects of process conditions upon the microstructure and mechanical properties of the joint and to also study/identify the joining mechanism. Two novel techniques were employed to join successfully the metal to ceramic. The first was by use of a thin Cu foil that did not remain after joining. Joining occurs by a process that results in partial melting of the Fecralloy interface, where Fe, Cr, Al and Cu reactively infiltrate into the silicon nitride. This liquid mixture causes partial dissolution of the silicon nitride interface, where Si and N diffuse into the Fecralloy. A thin reaction product layer was formed at the silicon nitride interface and our results suggested that this was AIN. The free surface Si and porosity of the silicon nitride along with the eutectic temperatures above 1100°C are all vital for this joining process. The highest average shear strength of a Fecralloy-silicon nitride joint produced by the method was 67.5 MPa. The second route was that of a powder metallurgy one, where cold pressed Ni-Al (1:1 molar) compacts were used to join successfully the Fecralloy to silicon nitride. The formation of NiAl from its constituents is highly exothermic and this is initiated between 500-650°C. The high temperature reached causes partial melting of the Fecralloy interface and dissolution/reactive wetting at the silicon nitride interface. Mostly Fe infiltrates the NiAl improving room temperature ductility, fracture toughness and yield strength. Molten Al from the interlayer reacts and wets the silicon nitride interface with small amount of infiltration and no reaction product forming. The reaction synthesis of NiAl was studied using DTA and TGA, where the effects of Ni particle size and heating rate were investigated. This joining process is highly dependant upon process conditions, the most important of which are applied pressure, heating rate and Ni/A1 particle size. The highest average shear strength attained was 94.30 MPa and this is attributed to good interfacial bonding, high pressure, moderate process temperature and dwell time. The exothermic formation of the NiAl interlayer that is densified and monophase was paramount for this joining process. The Bansal-Doremus kinetic model for evaluating the kinetic parameters from non-isothermal DTA data was shown to be valid. The results obtained were identical to those by other authors who used a different model and approach.
28
Wade, Jonathan. "High temperature and high pressure element partitioning between metal and silicate phases." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288307.
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29
Poloni, Roberta. "Heavy alkali metal-intercalated fullerenes under high pressure and high temperature conditions." Lyon 1, 2007. http://tel.archives-ouvertes.fr/docs/00/19/46/10/PDF/THESIS.pdf.
Повний текст джерелаАнотація:
Dans cette thèse nous explorons le diagramme de phase des fullerènes intercalées avec des métaux alcalins lourds, Rb6C60 et Cs6C60, à très haute pression (<50 GPa) et à très haute température (de l’ambiante à 1500 K). Ce travail inclue des expériences d’absorption de rayons X, de diffraction de rayons X, de spectroscopie Raman, ainsi que des calculs DFT ab initio à haute pression. Le couplage entre expériences et calculs permet d’observer que la présence de la forte interaction ionique entre chaque molécule et les ions alcalins, empêche la polymérisation des fullerènes sous pression. Dans le cas de Cs6C60, ceci a permis d’étendre le domaine de stabilité en pression des molécules de C60 d’au moins un facteur deux par rapport aux cristaux de C60 non-intercalés. Dans le cas de Rb6C60 une transition réversible est observée à 35 GPa. Nous avons mis en évidence la déformation progressive de la molécule de fullerène sous pression dans les systèmes étudiés. La compressibilité des deux cristaux a été mesurée et calculéeIn this thesis, we explore the phase diagram of the heavy alkali metal intercalated fullerenes, Rb6C60 and Cs6C60, under high pressure (<50 GPa) and high temperature conditions (from ambient to 1500 K). The work includes a series of X-ray absorption spectroscopy, X-ray diffraction and Raman spectroscopy measurements as well as ab initio DFT calculations under pressure. By coupling both experiments and calculations, we observed that the presence of strong ionic interactions between each molecule and the alkali metal ions, prevents fullerene polymerization under pressure. In the case of Cs6C60, this allows to extend the pressure stability of the C60 molecules more than twice with respect to pristine solid C60. In the case of Rb6C60 a phase transition, is observed at 35 GPa. A pressure induced enhanced deformation of the fullerene molecule in the studied systems has been evidenced. The compressibility of the both crystals has been measured and calculated
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Littleton, C. J. "Characterisation of high temperature corrosion products using Raman microscopy." Thesis, University of Newcastle upon Tyne, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378937.
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Darsell, Jens Tommy. "High temperature Ag-Pd-CuOx air braze filler metal." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Spring2007/J_Darsell_042607.pdf.
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Velasco, Pedro CorteÌs. "The mechanical properties of high temperature fibre-metal laminates." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421069.
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Fields, Mark. "Laser spectroscopy of metal halide vapours at high temperature." Thesis, University of Sheffield, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338154.
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Uberoi, Mohit. "High-temperature removal of metal vapors by solid sorbents." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185195.
Повний текст джерелаАнотація:
Emissions of metal vapor compounds during incineration and combustion is becoming an increasingly important problem. The kinetics and mechanism of high temperature removal of various metal vapors by solid sorbents has been investigated in this study. The kinetics experiments were performed in a high temperature microbalance reactor system under simulated flue gas atmosphere. Scanning electron microscopy, X-ray diffraction analysis, atomic absorption/emission spectrophotometry, Energy dispersive X-ray analysis, mercury porosimetry, and BET surface area analysis were used for characterization of the fresh and reacted sorbents. The results show that the process of metal vapor capture is not just physical condensation, but rather a complex combination of various chemical and physical processes. There are some similarities in the sorption process. For all the sorbents the rate of metal vapor sorption decreases with time and there is a final limit beyond which no more metal vapor gets captured. However, there are differences in the rate and reaction mechanism of metal vapor removal. Kaolinite and bauxite are suitable sorbents for lead and cadmium capture. The melting point of the lead aluminosilicate product formed after reaction of lead chloride with kaolinite and bauxite has a low melting point. Therefore, these sorbents are more suitable for downstream fixed bed removal of lead compounds. Removal of cadmium by bauxite occurs due to chemical reaction to form a cadmium aluminum silicate and a cadmium aluminate. Removal of cadmium by kaolinite occurs due to the formation of only the cadmium aluminosilicate. The final products of cadmium sorption have a higher water solubility as compared to that of the corresponding products for lead. Chlorine is not retained by the sorbents during the sorption process. Kaolinite, bauxite and emathlite are suitable sorbents for removal of alkali compounds. In adsorbing alkali chloride vapors, kaolinite and emathlite release all the chlorine back to the gas phase while bauxite retains some of the chlorine. Moreover, the products of reaction with emathlite have a melting point significantly lower than those for kaolinite and bauxite. At lower alkali concentrations, NaCl reacts irreversibly with kaolinite to form a sodium aluminosilicate product. When the local metal vapor concentration in the sorbent pores becomes higher than the saturation concentration for condensation, the metal vapor physically condenses in the sorbent pores and may subsequently react with the solid. The theoretical models developed were used to extract kinetic parameters from experimental data and for parametric studies. The kinetic data obtained can be used in design of practical metal removal systems.
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Liu, Weijie. "Advanced modelling for sheet metal forming under high temperature." Thesis, Troyes, 2017. http://www.theses.fr/2017TROY0019/document.
Повний текст джерелаАнотація:
L’objectif de cette thèse est de proposer deux approches complémentaires de modélisation et de simulation numériques des procédés de mise en forme de structures minces. La première est une approche inverse multi-pas, délibérément simplifiée, pour simuler et "optimiser" rapidement et à moindre coût des procédés d’emboutissage de tôles minces, tout en maintenant une bonne précision dans le calcul des contraintes. Un solveur statique implicite est développé en introduisant plusieurs configurations intermédiaires construites efficacement en utilisant une technique de programmation quadratique avec projection. La deuxième approche, de nature incrémentale, repose sur (i) une formulation d’équations de bilan et d’équations de comportement multi-physiques fortement couplés formulées dans le cadre des milieux micromorphes ; (ii) une discrétisation spatiale par EF et temporelle par DF avec un solveur global dynamique explicite et une intégration locale itérative implicite. Une attention particulière est accordée aux aspects thermiques avec l’introduction d’une microtempérature et ses premiers gradients conduisant à l’obtention de deux équations thermiques fortement couplées généralisant de nombreux modèles non locaux proposés dans la littérature. L'approche inverse multi-pas a été implémentée dans le code maison KMAS et l’approche incrémentale non locale a été implémentée dans ABAQUS/Explicit. Des études paramétriques sont menées et des validations sur des exemples simples et sur des procédés d’emboutissage sont réaliséesThe aim of this thesis is to propose two complementary approaches for modeling and numerical simulations of thin sheet metal forming processes. The first one is a deliberately simplified multi-step inverse approach to simulate and "optimize" rapidly and inexpensively thin-sheet stamping processes while maintaining good accuracy in the stress calculation. An implicit static solver is developed by introducing several efficiently constructed intermediate configurations using a quadratic programming technique with projection. The second approach, which is of an incremental nature, is based on (i) a formulation of equilibrium equations and strongly coupled multiphysical behavior equations formulated in the context of micromorphic continua; (ii) spatial discretization by FEM and time discretization by FD with an explicit dynamic global solver and implicit iterative local integration scheme. Particular attention is paid to the nonlocal thermal aspects with the introduction of a micro-temperature and its first gradients leading to two strongly coupled thermal equations generalizing several thermal nonlocal models proposed in the literature. The multi-step inverse approach was implemented in the KMAS in house code while the nonlocal incremental approach was implemented in ABAQUS/Explicit. Parametric studies are performed and validations are carried out on simple examples and on deep drawing processes
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Gregory, Paul David. "Mass spectrometry and matrix isolation of high temperature molecules." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261012.
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Jayasundera, Anil. "Solvothermal chemistry of luminescent lanthanide fluorides." Thesis, University of St Andrews, 2009. http://hdl.handle.net/10023/2125.
Повний текст джерелаАнотація:
Exploration of novel lanthanide fluoride framework materials in inorganic-organic hybrid systems under solvothermal conditions towards development of new luminescent materials is discussed. X-ray single crystal and powder diffraction methods have been used as crystallographic characterisation techniques. Determination and study of luminescence properties for selected hybrid materials has also been carried out. The first organically templated luminescent lanthanide fluoride framework, [C₂N₂H₁₀]₀.₅ [Ln₂F₇] (Ln= Nd, Tb, Dy, Ho, Er, Yb and Lu), has been synthesised and characterised. This structure type consists of a three-dimensional yttrium fluoride framework incorporating two similar, but crystallographically distinct, yttrium sites. Photoluminescence studies of [C₂N₂H₁₀]₀.₅ [Y₂F₇]: Ln³⁺ (Ln³⁺ = Gd³⁺, Eu³⁺ and Tb³⁺) have been explored and characteristic luminescence emissions are reported. An inorganic-organic hybrid indium fluoride and its scandium fluoride analogue, [C₄H₁₄N₂][MF₅](M=In and Sc) is reported. The structure consists of infinite trans vertex sharing (InF₅)[subscript(∞)] chains, which are linked via H-bonded organic moieties. The scandium and fluorine local environments of [C₄H₁₄N₂][ScF₅] are characterised by ¹⁹F, and ⁴⁵Sc solid-state MAS NMR spectroscopies. A single scandium site has been confirmed by ⁴⁵Sc MAS NMR. ¹⁹F MAS NMR clearly differentiates between bridging and terminal fluorine. The photoluminescence properties of these complexes, [C₄H₁₄N₂][In[subscript(1-x)] Ln[subscript(x)]F₅] (Ln=Tb and/or Eu), have been explored. The optimum composition for Eu³⁺ doped samples occurs at x = 0.05 Eu³⁺ and the “asymmetry ratio” of R = I₅₉₀/I₆₁₅ ( ⁵D₀ → ⁷F₂ and ⁵D₀ → ⁷F₁) gives a clear picture of the sensitivity for crystal field of the compound. For x = 0.08 Tb³⁺, a strong down-conversion fluorescence corresponding to ⁵D₄ → ⁷F₅ (green at 543.5 nm) occurs. In addition, a Tb³⁺/Eu³⁺ co-doped sample exhibits a combination of green (Tb³⁺) and orange (Eu³⁺) luminescence, with Tb³⁺ enhancing the emission of Eu³⁺ in this host. Exploration of novel indium, aluminium, and zirconium fluoride crystal structures with potential luminescent properties has also been undertaken. A chiolite-like phase K₅In₃F₁₄ (space group P4/mnc) has been synthesised. No phase transition occurs over the temperature range 113K< T< 293 K, as has been seen in other chiolite-like structures. An organically templated indium fluoride, [NH₄]₃[C₆H₂₁N₄]₂[In₄F₂₁] has been prepared; this features the trimeric unit [In₃F₁₅]³⁻ which appears to be the first of its type in a metal fluoride. A new hybrid fluoride, Sr[N₂C₂H₁₀]₂[Al₂F₁₂].H₂O has been synthesised. Because the ionic radius of Eu²⁺ is similar to that of Sr ²⁺ this may be a potential host for blue luminescent Eu²⁺. The new material KZrF₅.H₂O shows pentagonal-bipyramidal geometry of Zr⁴⁺ with a polar space group, Pb2₁m, which may potentially have ferroelectric properties.
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Abel, Godard Karl. "Design and construction of high temperature uniform metal spray apparatus." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/17316.
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Wilk, Gregory. "Liquid metal based high temperature concentrated solar power: Cost considerations." Thesis, Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54937.
Повний текст джерелаАнотація:
Current concentrated solar power plants (CSP) use molten salt at 565°C as a heat transfer and energy storage fluid. Due to thermal energy storage (TES), these solar plants can deliver dispatachable electricity to the grid; however, the levelized cost of electricity (LCOE) for these plants is 12-15 c/kWh, about 2.5 times as high as fossil fuel electricity generation. Molten salt technology limits peak operating temperatures to 565°C and a heat engine efficiency of 40%. Liquid metal (LM), however, can reach >1350°C, and potentially utilize a more efficient (60%) heat engine and realize cost reductions. A 1350 °C LM-CSP plant would require ceramic containment, inert atmosphere containment, additional solar flux concentration, and redesigned internal receiver. It was initially unclear if these changes and additions for LM-CSP were technically feasible and could lower the LCOE compared to LS-CSP. To answer this question, a LM-CSP plant was designed with the same thermal input as a published LS-CSP plant. A graphite internal cavity receiver with secondary concentration heated liquid Sn to 1400°C and transferred heat to a 2-phase Al-Si fluid for 9 hours of thermal energy storage. Input heat to the combined power cycle was 1350°C and had 60% thermal efficiency for a gross output of 168 MW. The cost of this LM-CSP was estimated by applying material cost factors to the designed geometry and scaling construction costs from published LS-CSP estimates. Furthermore, graphite was experimentally tested for reactivity with liquid Sn, successful reaction bonds, and successful mechanical seals. The result is switching to molten metal can reduce CSP costs by 30% and graphite pipes, valves, and seals are possible at least at 400°C.
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Lipke, David William. "Novel reaction processing techniques for the fabrication of ultra-high temperature metal/ceramic composites with tailorable microstructures." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/43750.
Повний текст джерелаАнотація:
Ultra-high temperature (i.e., greater than 2500°C) engineering applications present continued materials challenges. Refractory metal/ceramic composites have great potential to satisfy the demands of extreme environments (e.g., the environments found in solid rocket motors upon ignition), though general scalable processing techniques to fabricate complex shaped parts are lacking. The work embodied in this dissertation advances scientific knowledge in the development of processing techniques to form complex, near net-shape, near net-dimension, near fully-dense refractory metal/ceramic composites with controlled phase contents and microstructure.
Three research thrusts are detailed in this document. First, the utilization of rapid prototyping techniques, such as computer numerical controlled machining and three dimensional printing, for the fabrication of porous tungsten carbide preforms and their application with the Displacive Compensation of Porosity process is demonstrated. Second, carbon substrates and preforms have been reactively converted to porous tungsten/tungsten carbide replicas via a novel gas-solid displacement reaction. Lastly, non-oxide ceramic solid solutions have been internally reduced to create intragranular metal/ceramic micro/nanocomposites. All three techniques combined have the potential to produce nanostructured refractory metal/ceramic composite materials with tailorable microstructure for ultra-high temperature applications.
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Hrubiak, Rostislav. "Exploring Thermal and Mechanical Properties of Selected Transition Elements under Extreme Conditions: Experiments at High Pressures and High Temperatures." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/696.
Повний текст джерелаАнотація:
Transition metals (Ti, Zr, Hf, Mo, W, V, Nb, Ta, Pd, Pt, Cu, Ag, and Au) are essential building units of many materials and have important industrial applications. Therefore, it is important to understand their thermal and physical behavior when they are subjected to extreme conditions of pressure and temperature. This dissertation presents: An improved experimental technique to use lasers for the measurement of thermal conductivity of materials under conditions of very high pressure (P, up to 50 GPa) and temperature (T up to 2500 K). An experimental study of the phase relationship and physical properties of selected transition metals, which revealed new and unexpected physical effects of thermal conductivity in Zr, and Hf under high P-T. New phase diagrams created for Hf, Ti and Zr from experimental data. P-T dependence of the lattice parameters in α-hafnium. Contrary to prior reports, the α-ω phase transition in hafnium has a negative dT/dP slope. New data on thermodynamic and physical properties of several transition metals and their respective high P-T phase diagrams. First complete thermodynamic database for solid phases of 13 common transition metals was created. This database has: All the thermochemical data on these elements in their standard state (mostly available and compiled). All the equations of state (EoS) formulated from pressure-volume-temperature data (measured as a part of this study and from literature). Complete thermodynamic data for selected elements from standard to extreme conditions.
The thermodynamic database provided by this study can be used with available thermodynamic software to calculate all thermophysical properties and phase diagrams at high P-T conditions. For readers who do not have access to this software, tabulated values of all thermodynamic and volume data for the 13 metals at high P-T are included in the APPENDIX. In the APPENDIX, a description of several other high-pressure studies of selected oxide systems is also included.
Thermophysical properties (Cp, H, S, G) of the high P-T ω-phase of Ti, Zr and Hf were determined during the optimization of the EoS parameters and are presented in this study for the first time. These results should have important implications in understanding hexagonal-close-packed to simple-hexagonal phase transitions in transition metals and other materials.
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Winand, Henri Michel Andre. "Damage, internal stresses and high temperature behaviour of metal matrix composites." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286674.
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Baskar, Dinesh. "High temperature magnetic properties of transition metal oxides with perovskite structure /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/9812.
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Markkula, Mikael. "Synthesis, structure and properties of high pressure and ambient pressure ternary vanadium oxides." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/8061.
Повний текст джерелаАнотація:
Transition metal oxides have been extensively studied during past decades. The purpose of this research was to synthesize new or little characterised transition metal oxides using high-pressure/high-temperature (HPHT) techniques. Various ternary vanadium oxides have been synthesised at ambient and high pressure conditions. All compounds have been studied by neutron and laboratory X-ray powder diffraction and magnetisation measurements. In some cases resistivity and synchrotron X-ray powder diffraction measurements were also carried out. The MnVO3 perovskite containing localized 3d5 Mn2+ and itinerant 3d1 V4+ states has been synthesised at 8 GPa and 1100°C. MnVO3 crystallises in Pnma space group (a = 5.2741(6) Å, b = 7.4100(11) Å, and c = 5.1184(8) Å at 300 K) and is metallic at temperatures of 2 – 300 K and at pressures of up to 67 kbar. Synchrotron X-ray powder diffraction study on the combined sample of several high pressure products showed slight variation in the stoichiometry of MnVO3. Incommensurate Mn spin order was discovered in the neutron powder diffraction measurements, which reveal a (0.29 0 0) magnetic vector below the 46 K spin ordering transition, and both helical and spin density wave orderings are consistent with the diffraction intensities. Electronic structure calculations show large exchange splittings of the Mn and V 3d bands, and (kx 0 0) crossings of the Fermi energy by spin up and down V 3d bands may give rise to Ruderman-Kittel-Kasuya-Yosida coupling of Mn moments, in addition to their superexchange interactions. The new compound CoVO4 has been discovered in a high pressure synthesis experiment. Magnetic susceptibility measurement, synchrotron X-ray and neutron powder diffraction studies were carried out. Refinements of the synchrotron X-ray and neutron data show CoVO4 to crystallise in space group Pbcn (a = 4.5012(2) Å, b = 5.5539(3) Å, and c = 4.8330(2) Å at 300 K (synchrotron X-ray data)). The magnetic susceptibility measurement reveals that Co3+ is most likely in a low spin state in CoVO4. Monoclinic brannerite type CoV2O6 was synthesised in ambient pressure. Neutron powder diffraction measurements were carried out and an antiferromagnetic order with an a x b x 2c supercell was observed below TN = 15 K. High spin Co2+ moments of magnitude 4.77(4) μB at 4 K lie in the ac plane and are ferromagnetically coupled within chains of edge-sharing CoO6 octahedra parallel to b axis. No structural transition is observed down to 4 K, but a magnetostriction accompanying antiferromagnetic order at TN = 15 K was discovered. A field-induced 1/3 magnetisation plateau and corresponding changes in the magnetic structure were studied by carrying out neutron powder diffraction measurements at 2 K in applied magnetic fields of 0, 2.5 and 5.0 T. Three collinear magnetic phases were observed as field increases; the above antiferromagnetic state with propagation vector (0 0 ½), a ferrimagnetic (¯⅓ 1 ⅓) phase, and a (0 0 0) ferromagnetic order. Co2+ moments of 4.4 - 5.0 μB have a large orbital component and are aligned close to the c-axis direction in all cases. Spin-lattice coupling leads to a magnetostriction and volume expansion as field increases. The ferrimagnetic phase accounts for the previously reported 1/3 magnetisation plateau, and demonstrates that monoclinic CoV2O6 behaves as an accidental triangular antiferromagnetic lattice in which further frustrated orders may be accessible. Orthorhombic columbite-type NiV2O6 and CoV2O6 compounds were synthesised at 6 GPa and 900°C. Metamagnetism and magnetic transitions were found in magnetic measurements. Powder neutron diffraction studies in zero and applied field were carried out. Both compounds were refined in space group Pbcn and the following lattice parameters were obtained at 300 K, CoV2O6: a = 13.4941(20) Å, b = 5.5736(9) Å, and c = 4.8082(8) Å and NiV2O6: a = 13.3725(17) Å, b = 5.5344(7) Å, and c = 4.8162(7) Å. Neutron powder diffraction studies in zero field did not reveal any magnetic peaks for either of the compounds but magnetic order emerges in applied fields between 1 and 4 T.
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Håkansson, Kenneth. "Weld Metal Properties for Extra High Strength Steels." Doctoral thesis, KTH, Production Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3403.
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Rand, Timothy Rand. "Investigation into sintering and melt-growing of high temperature superconducting 123 materials." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242455.
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Thiesing, Benjamin P. "High temperature measurements of surface changes in metal alloys using digital holography." Thesis, Northern Arizona University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1537812.
Повний текст джерелаАнотація:
Digital Holography (DH) is an emerging tool for use in the structural investigation of temperature dependent material processes. DH is able to reveal deformations and topological details at ultrahigh sensitivity (a few tens of nanometers) for particular details such as point-like objects and interfacial structures, allowing for the investigation of a range of processes. However, while DH is able to provide high precision data, the height measurement range is limited by the probe wavelength. Therefore a 'synthetic' wavelength created from the superposition of two or more individual wavelengths is often required in order to increase the measurement range to a suitable value dependent upon the object dimensions.
The use of multiple wavelengths attached to one system thus allows for surface height measurements over a relatively long range. In addition as the complex wave-front of each wavelength can be captured simultaneously in one digital image, real-time performance is achievable. In this thesis a number of materials processes were investigated at differing temperatures. The structural changes associated with the martensite to austenite phase transformation were measured using dual-wavelength digital holography during thermal cycling of nickel-aluminum-platinum (NiAlPt) and single-crystal Fe-15Cr-15Ni alloys. Real-time in-situ measurements reveal the formation of striations within the NiPtAl alloy at ∼70°C, and the FeCrNi alloy at ∼520°C. The results demonstrate that digital holography is an effective technique for acquiring non-contact, high precision information of the 3D surface evolution of alloys at high temperatures.
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Crabb, T. A. "Advanced surface sensitive X-ray techniques : application to the study of the initial stages of high temperature corrosion of metals and alloys." Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297323.
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Deangelis, Alfred N. "Analysis and design of a high temperature liquid metal solar thermal receiver." Thesis, Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55063.
Повний текст джерелаАнотація:
Current concentrated solar technologies are not cost-effective means of generating electricity and would benefit greatly from higher operating temperatures. To reach these temperatures at high efficiencies, a novel receiver design should be used in the plant. As a first step in the design of such a receiver, a sensitivity analysis is useful to determine what parameters most affect the performance of a generic cavity receiver. The results of this sensitivity analysis can be used to develop an optimized cavity receiver geometry intended to operate at a high efficiency (>80%) at extreme temperatures (1,350°C). It was found that limiting re-radiation and convection through the cavity aperture most improve the performance of the receiver; at the same time, the receiver must be designed in such a way as to minimize thermal stresses. Descriptions of many experimental components that have been developed to allow for a successful test of a laboratory scale receiver are also included in this thesis. Additionally, presented here are the results of some initial experiments intended to validate the simulations used to perform the aforementioned sensitivity analysis. Finally, some remarks are proffered detailing additional steps and considerations necessary to scale up the receiver design to an industrial scale.
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Tripp, David William. "The thermal regime during electron beam hearth remelting." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26748.
Повний текст джерелаАнотація:
Electron beam hearth remelting is extensively used in refining of superalloys, titanium alloys and the recycling of these materials. The removal of impurities and exhogenous particles during the hearth melting operation depends primarily on the time at temperature relationship developed within a pool of molten metal. In the past hearth melters have acted largely on empirical evidence to specify such parameters as melt rates, power levels and skull sizes. This work describes a mathematical model which could be used to predict certain parameters (such as pool volume or alloy element evaporation rates) when given skull geometry, power input and melt rate.
A three dimensional steady state heat transfer model of both the skull and water cooled copper mould during electron beam hearth remelting has been developed. The model has been used to investigate the effects of surface temperature, liquid motion, power input, skull geometry, presence of the hearth mould and melt rate on parameters such as pool volume during skull melting.
In general the choice of any combination of operating parameters depends on a balance between the refining capacity of the process (i.e. liquid volume) and the loss of alloy elements by evaporation. In the case of melting pure materials (e.g. CP titanium) the balance is between refining capacity and efficient energy use.
It was found that forced convection is significantly more effective in increasing the volume of the liquid pool than any other single parameter. Increasing the power input to the skull, increasing the skull width and removing the water cooled copper mould from around the skull also increase the pool volume. The evaporation rates of alloy elements within the skull were most effected by changes in the power distribution and the degree of liquid motion.Applied Science, Faculty of
Materials Engineering, Department of
Graduate