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1
Wilder, Corey B. "Study of tungsten(IV) and tungsten(VI) imido complexes synthesis, structural analysis, and reactivity /." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0011630.
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Engwall, Alison Michelle. "Atomistic computer simulation analysis of nanocrystalline nickel-tungsten alloys." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/57674.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2009.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 31).<br>Nanocrystalline nickel-tungsten alloys are harder, stronger, more resistant to degradation, and safer to electrodeposit than chromium. Atomistic computer simulations have previously met with success in replicating the energetic and atomic conditions of physical systems with 2-4nm grain diameters. Here, a new model subjects a vertically thin unique volume containing 3nm or 10nm FCC grains with aligned z axes to a Monte Carlo-type minimization to investigate the segregation and ordering behavior of W atoms. Short-range order is also tracked with the Warren-Cowley parameter, and energetic results are explored as well. It was found that the Ni-W system has a very strong tendency toward SRO. The 10nm models exhibited more robust order at low concentrations, but ordering in the 3nm model was generally more pronounced. At the dilute limit atoms are driven to the grain boundaries, but as the boundaries are saturated intragranular ordered formations increase and may even perpetuate over low-angle grain boundaries. Ordering was also observed within the grain boundaries at all concentrations for both diameters. The 10nm models were saturated at lower concentration, and grain boundary energy was reduced by up to 93%. W atoms preferred to associate with each other as third-nearest neighbors, but at very high concentrations formations with W atoms as second nearest neighbors were also observed.<br>by Alison Michelle Engwall.<br>S.B.
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Yi, X. "Electron microscopy study of radiation damage in tungsten and alloys." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:cb416551-164d-4290-b134-83278708ceff.
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The displacement damage induced by primary recoils of fusion neutrons in tungsten and alloys has been studied with self-ion irradiations, followed by damage characterization with electron microscopy. Tungsten and alloys (≤ 5 wt.% Re, Ta, V) were implanted with 2 MeV W+ ions over a dose range of 3.3×1017 - 2.5×1019 W+m-2 at temperatures ranging from 300 to 750°C. Dislocation loops of b = ½<111> (> 60%) and b = <100> were identified, and that ½<111> loops were found more thermally stable. Among loops that were large enough for nature determination, at least 50% were found to be of interstitial type, with larger fractions in high-temperature and high-dose conditions. The diameter of loops did not exceed 20 nm, with the majority being ≤ 5 nm. The loop number density varied between 1022 and 1023 m-3. The effects of ion dose, irradiation temperature, composition and grain orientation on damage microstructure were investigated. In-situ irradiations (150 keV W+ ions) were carried out as a complement to the bulk implantations. Qualitative trends in loop size, geometry and nature with irradiation dose and temperature were similar to bulk irradiated specimens. Also, the dynamics of defects and their effects on the damage evolution were explored. In-situ annealing of irradiated thin foils was performed to investigate the thermal stability of radiation damage in tungsten. The majority of microstructure transformations were completed within 15 min of annealing. However, extended durations did favour the increase of loop size and the fraction of ½<111> loops.
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Sen, Debamoy. "Coupled Field Modeling of Gas Tungsten Arc Welding." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/38820.
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Welding is used extensively in aerospace, automotive, chemical, manufacturing, electronic and power-generation industries. Thermally-induced residual stresses due to welding can significantly impair the performance and reliability of welded structures. Numerical simulation of weld pool dynamics is important as experimental measurements of velocities and temperature profiles are difficult due to the small size of the weld pool and the presence of the arc. From a structural integrity perspective of welded structures, it is necessary to have an accurate spatial and temporal thermal distribution in the welded structure before stress analysis is performed. Existing research on weld pool dynamics simulation has ignored the effect of fluid flow in the weld pool on the temperature field of the welded joint. Previous research has established that the weld pool depth/width (D/W) ratio and Heat Affected Zone (HAZ) are significantly altered by the weld pool dynamics. Hence, for a more accurate estimation of the thermally-induced stresses it is desired to incorporate the weld pool dynamics into the analysis. Moreover, the effects of microstructure evolution in the HAZ on the mechanical behavior of the structure need to be included in the analysis for better mechanical response prediction. In this study, a three-dimensional model for the thermo-mechanical analysis of Gas Tungsten Arc (GTA) welding of thin stainless steel butt-joint plates has been developed. The model incorporates the effects of thermal energy redistribution through weld pool dynamics into the structural behavior calculations. Through material modeling the effects of microstructure change/phase transformation are indirectly included in the model. The developed weld pool dynamics model includes the effects of current, arc length, and electrode angle on the heat flux and current density distributions. All the major weld pool driving forces are included, namely surface tension gradient, plasma drag force, electromagnetic force, and buoyancy. The weld D/W predictions are validated with experimental results. They agree well. The effects of welding parameters (like welding speed, current, arc length, etc.) on the weld D/W ratio are documented. The workpiece deformation and stress distributions are also highlighted. The transverse and longitudinal residual stress distribution plots across the weld bead and their variations with welding speed and current are also provided. The mathematical framework developed here serves as a robust tool for better prediction of weld D/W ratio and thermally-induced stress evolution and distribution in a welded structure by coupling the different fields in a welding process.<br>Ph. D.
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Shakya, Reema. "Development of a Direct Analysis Method for Copper in Serum by Tungsten Filament Electrothermal Atomic Absorption." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1571929.
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<p> The analysis of horse serum samples for copper is relevant to biomarkers for a variety of pathologies in humans. The inexpensive and compact nature of locally laboratory built tungsten filament electrothermal atomic absorption spectrometry instruments (WETAAS) makes them well suited to copper analysis in the clinical context; however, little research in this area exists. This project was undertaken to determine the experimental conditions necessary for determining copper in serum by WETAAS without resorting to sample digestion. Serum samples were prepared by 1:5 dilution in 0.2% nitric acid solution. The filament positioning with the light path plays an important role in the actual number of vaporized atoms of analyte being detected. In aqueous calibration standards, ammonium dihydrogen phosphate was found to be a critical matrix modifier, but in the presence of serum as an interference, the matrix modifier was not of much use. The results indicate that the serum matrix strongly suppresses the copper analytical signal. The merits of using integrated area for quantitation rather than peak height was found in the complex matrix system. Then the background concentration of copper in serum was determined by the standard additions method. Then the same samples were analyzed using a standard method for analysis of copper in serum through flame atomic absorption spectrometry, which is a matrix interference independent system.</p>
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Love, Bryan Matthew. "Multiscale Analysis of Failure in Heterogeneous Solids Under Dynamic Loading." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29650.
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Plane strain transient finite thermomechanical deformations of heat-conducting particulate composites comprised of circular tungsten particulates in nickel-iron matrix are analyzed using the finite element method to delineate the initiation and propagation of brittle/ductile failures by the nodal release technique. Each constituent and composites are modeled as strain hardening, strain-rate-hardening and thermally softening microporous materials. Values of material parameters of composites are derived by analyzing deformations of a representative volume element whose minimum dimensions are determined through numerical experiments. These values are found to be independent of sizes and random distributions of particulates, and are close to those obtained from either the rule of mixtures or micromechanics models.
Brittle and ductile failures of composites are first studied by homogenizing their material properties; subsequently their ductile failure is analyzed by considering the microstructure. It is found that the continuously varying volume fraction of tungsten particulates strongly influences when and where adiabatic shear bands (ASB) initiate and their paths. Furthermore, an ASB initiates sooner in the composite than in either one of its constituents.
We have studied the initiation and propagation of a brittle crack in a precracked plate deformed in plane strain tension, and a ductile crack in an infinitely long thin plate with a rather strong defect at its center and deformed in shear. The crack may propagate from the tungsten-rich region to nickel-iron-rich region or vice-a-versa. It is found that at the nominal strain-rate of 2000/s the brittle crack speed approaches Rayleigh's wave speed in the tungsten-plate, the nickel-iron-plate shatters after a small extension of the crack, and the composite plate does not shatter; the minimum nominal strain-rate for the nickel-iron-plate to shatter is 1130/s. The ductile crack speed from tungsten-rich to tungsten-poor regions is nearly one-tenth of that in the two homogeneous plates. The maximum speed of a ductile crack in tungsten and nickel-iron is found to be about 1.5 km/s.
Meso and multiscale analyses have revealed that microstructural details strongly influence when and where ASBs initiate and their paths. ASB initiation criteria for particulate composites and their homogenized counterparts are different.<br>Ph. D.
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Archer, M., RI McCrindle, and ER Rohwer. "Analysis of cobalt, tantalum, titanium, vanadium and chromium in tungsten carbide by inductively coupled plasma-optical emission spectrometry." The Royal Society of Chemistry, 2003. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001953.
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Summary
Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to measure the concentrations
of cobalt, tantalum, titanium, vanadium and chromium in solutions of tungsten carbide. The main advantage
of the method described here lies in the speed, convenience and effectiveness of the dissolution procedure.
Aliquots of powdered tungsten carbide were dissolved in a solution of 5% aqua regia in 30% hydrogen
peroxide. Complete dissolution was usually achieved within 10 min. The accuracy of the method was assessed
by the analysis of certified reference materials, secondary reference materials and matrix spiking. The method
was successfully applied to commercial type samples with differing compositions. Slightly more emphasis was
placed on the measurement of vanadium, since no information on the measurement of this element in solutions
of tungsten carbide, by ICP-OES, has been published. Investigation of the interference effects of the elements in
the sample matrix on each other was essential for accurate results comparable to other published analytical
methods.
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Bettinelli, Armand. "Cofrittage de l'alumine et du tungstene a 1400 non= c." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13144.
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Fabrication des ensembles multicouches ayant pour role la protection et l'interconnexion des circuits integres. Diminution de la temperature de cofrittage de 1600 a 1400 non=c. Etude de cofrittage realisee sur des bandes d'alumine coulees par "tape casting" puis serigraphiees
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Trueman, Anthony Roger. "Characterization and corrosion studies of high carbon tool steel/tungsten carbide metal matrix composites." Thesis, Queensland University of Technology, 1999.
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Denizer, Baris. "Artificial neural network analysis of the mechanical properties of tungsten fiber/bulk metallic glass matrix composites via neutron diffraction and finite element modeling." [Ames, Iowa : Iowa State University], 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1461844.
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Owais, Tariq Muhammad. "Impact of pressure on Sintering of Cemented Carbides." Thesis, KTH, Materialvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-123170.
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In this Master Thesis work, the effect of pressure on sintering of cemented carbides is investigated. Special focus hasbeen given to the residual porosity after sintering. It is well known that sintering shrinkage depends on binder phasecontent, grain size, temperature and pressure. Thus 4 different cemented carbides grades were selected. The gradeswere pressed into standard products and TRS (Tensile Rupture Strength) rods with two different shrinkage factors.These were then sintered at different pressures and temperatures. Thereafter the impact of pressure on propertiessuch as Density, Coercivity, Porosity and TRS were analyzed. The observations were further supported with Weibullprobability analysis and fracture surface analysis in SEM.It has been shown that there exists a distinct threshold pressure at which significant reduction in porosity occurs forgiven compacted densities. For 3 out of 4 cemented carbide grades it has been observed that P2 sintering pressure issufficient to meet desired product characteristics. The fourth grade required a minimum sintering pressure of P4 toachieve desired quality criteria. Moreover it has been concluded that an increased sintering pressure increasesmaterial strength, as compared to vacuum sintering, thereby reducing the amount of early failures caused by poresduring TRS test. Keywords: Cemented Carbides, Pressurized Sintering, Tungsten carbide, Porosity, Vacuum sintering, TensileRupture Strength, Weibull analysis, Fracture surface analysis.
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BAULY, JULIO C. "Caracterizacao microestrutural e propriedades de juntas dissimilares entre acos inoxidaveis fabricados por processos de fusao." reponame:Repositório Institucional do IPEN, 2000. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10832.
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06907.pdf: 7394695 bytes, checksum: bde9c680792583e55f4754af5867fe98 (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Lenzo, Jansen C. Lenzo. "Evaluation of the Effect of Tungsten and Boron Additions on the Microstructure and Solidification Cracking Susceptibility of Fe-Mn-C Filler Metals." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1470829433.
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Sarrazit, Franck. "Structure of grain boundaries in hexagonal materials." Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367291.
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Reisinger, Sandra A. "Synthesis and structure-property relationships in selected metal fluorides." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/2030.
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There has been an increase in the interest in fluoride materials over the last decade. This interest has focused on multiferroic materials and kagome lattices, to name but a few areas. This thesis focuses on the synthesis and crystallographic characterisation of selected transition metal fluorides and oxyfluorides. Work is presented on the tetragonal tungsten bronze solid solutions of KₓFeF₃, where x = 0.58 and x ≈ 0.5, and the copper analogue, K₃Cu₃Fe₂F₁₅; the kagome structure of Cs₂ZrCu₃F₁₂; and hydrothermal reactions using vanadium, manganese, or molybdenum as the transition metals in the formation of new fluorides and oxyfluorides. The tetragonal tungsten bronze compounds KₓFeF₃ (x = 0.58 and x ≈ 0.5) are both tetragonal at 500 K. In the variant with the lower K-content, there is a clear phase separation into two tetragonal phases even at this temperature. The K₀.₅₈FeF₃ sample separates into two distinct phases below 340 K to possess one tetragonal and one orthorhombic phase. Then at roughly 300 K, both samples undergo a phase transition where the tetragonal phase in the P4/mbm space group in K₀.₅₈FeF₃ changes to an orthorhombic phase with a larger unit cell; and the tetragonal phase in P4₂bc for the K₀.₅FeF₃ sample changes to the same orthorhombic model, whilst the P4/mbm model remains unchanged. The evolution of the lattice parameters and phase fractions is studied in detail using synchrotron powder X-ray diffraction (sPXRD). The kagome structure investigated, Cs₂ZrCu₃F₁₂, possesses the “ideal” kagome lattice at room temperature, but previous work has suggested that there is a phase transition at 225 K. The two structures are determined by single crystal X-ray diffraction at 300 K and 125 K. Variable temperature sPXRD studies are performed between these two temperature ranges to determine the phase evolution as a function of temperature. The structure changes from a rhombohedral to a monoclinic phase at low temperature. This is the result of the buckling of the kagome layers at the phase transition. The Zr⁴⁺ ion changes from 6 to 7 coordinate and this is seen as the main driving force for the distortion of the kagome layer from its “ideal” planar arrangement. ii The phase transition is first-order as seen from the electrical impedance measurements. The hydrothermal reactions presented reveal seven new materials and their crystal structures. Sr₂V₂F₁₀·H₂O is new and found to be isostructural to Sr₂Fe₂F₁₀·H₂O. BaVO₂F₃ is a cubic material that is potentially piezoelectric. Two hybrid organic inorganic manganese compounds are reported. The ladder structure (C₃N₂H₅)[Mn₂F₆(H₂O)₂] crystallises in a polar space group and shows promise as a candidate for multiferroic studies. The second hybrid material, (C₇NH₁₆)₂[MnF₅(H₂O)]·2H₂O, crystallises in a centrosymmetric space group. The Mo hybrid materials are all centrosymmetric and possess isolated molybdenum-centred monomeric or dimeric octahedral units.
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HIGASHI, CRISTIANE. "Investigação do processo de obtenção de aluminatos de bário e cálcio para construção e caracterização de catodos termiônicos impregnados para a aplicação em dispositivos de microondas de potência." reponame:Repositório Institucional do IPEN, 2006. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11463.
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Novotný, Petr. "Technicko-ekonomické řešení nožů odkorňovače." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228067.
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The target of the study is theoretical explaining the condition of creation of the soldered point with regard to basic and additional mat. Below, the detailed analysis of the existing technical problem and consecutive design of the solution method.Content of the study is also technological process of production of the barking knife and choice of the efficient producer.
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Roure, Sophie. "Densification des mélanges de poudres WC-Co : de la compression au frittage." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0222.
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Ce travail a pour objectif de prevoir le comportement des melanges wc-co lors du compactage et leur evolution au cours du frittage, en s'interessant particulierement a l'influence de la geometrie des microstructures sur la densification du materiau. Lors de l'etude macroscopique de la compression a froid, un test de compressibilite est etabli pour caracteriser l'aptitude de ces melanges a se comprimer selon les parametres de la poudre et les conditions de l'essai. Ce test fournit une loi de compressibilite intrinseque du melange et un coefficient relatif a la fluidite de la poudre et a son frottement aux parois. Les resultats des essais effectues sont interpretes a l'aide d'une analyse micromecanique du comportement d'empilements composites de particules. Au cours du frittage, l'etude macroscopique de la densification par dilatometrie determine l'evolution du retrait en fonction des parametres du procede, des caracteristiques du melange et de la densite a vert. Un interet particulier est porte a la part de densification realisee en phase solide. On montre que celle-ci est reliee a un rearrangement des grains wc qui se poursuit jusqu'a la formation d'un empilement stable de ces grains. En parallele, une etude microscopique quantitative par analyse d'images caracterise les etats comprime et fritte et l'evolution d'un etat a un autre. Elle permet d'etablir qu'en phase solide l'ecoulement du liant et le rearrangement des grains wc sont deux phenomenes simultanes. Finalement, une modelisation de la densification des melanges wc-co est proposee, qui integre les caracteristiques geometriques instantanees de l'empilement, propres au systeme etudie, au sein d'une approche cinetique globale simple
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OLIVEIRA, EDUARDO S. "Ablação seletiva de um filme de nitreto de titânio em substrato de carboneto de tungstênio utilizando laser de pulsos ultracurtos." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/27976.
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Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2017-11-09T11:36:10Z
No. of bitstreams: 0<br>Made available in DSpace on 2017-11-09T11:36:10Z (GMT). No. of bitstreams: 0<br>Revestimentos superficiais são aplicados à muitas ferramentas de usinagem na indústria metalúrgica com o intuito de melhorar a eficiência de corte e aumentar sua vida útil. Neste trabalho foram realizados testes para remoção do recobrimento de nitreto de titânio alumínio (TiAlN) em pastilhas de carboneto de tungstênio (WC-Co), utilizando um feixe laser de pulsos ultracurtos. Após a determinação dos limiares de dano do filme e do substrato foram ablacionados na superfície do recobrimento, traços utilizando duas condições de ablação. Inicialmente operou-se no regime de baixa fluência do filme, e posteriormente no regime de baixa fluência do substrato, muito abaixo do limiar do filme, aplicando-se alta sobreposição de pulsos. Um sistema de espectroscopia de emissão atômica induzida por laser (LIBS) foi montado para monitoramento dos materiais presentes no plasma gerado pelo laser, porém o sistema não apresentou sensibilidade suficiente para leitura da baixa intensidade do plasma proveniente do processo e não foi utilizado. Após a análise dos traços por microscopia eletrônica, perfilometria óptica e espectroscopia por fluorescência de Raios-X, não foi possível determinar um processo seguro para realizar a remoção seletiva do filme em questão, porém, devido aos dados obtidos e observações dos resultados em alguns traços, novas possibilidades foram levantadas, abrindo a discussão para a realização de trabalhos futuros.<br>Dissertação (Mestrado em Tecnologia Nuclear)<br>IPEN/D<br>Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Bunte, Henning. "Der Einfluß der Ausarbeitung mit verschiedenen rotierenden Instrumenten auf die Randqualität und Oberflächenmorphologie von zahnfarbigen lichthärtenden Restaurationen." Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2001. http://dx.doi.org/10.18452/14671.
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In dieser Studie wurde das Verhalten eines neuentwickelten Hartmetallfinierers der Firma Brasseler und herkömmlicher grober und feiner Diamantfinierer der Firmen Intensiv und Brasseler an vier verschiedenen Füllungsmaterialien untersucht. Bei dem Hartmetallfinierer handelt es sich um ein Kombinationsinstrument, das sich im Rechtslauf durch eine hohe Arbeitsleistung auszeichnet und zum Konturieren von Füllungen gedacht ist. Im Linkslauf soll das Instrument zur Feinausarbeitung eingesetzt werden, die Arbeitsleistung ist geringer. In 120 extrahierte menschliche Zähne wurden ovale Klasse-V-Kavitäten (Länge: 4 mm, Breite: 3 mm, Tiefe: 2 mm) präpariert, die jeweils zur Hälfte im Schmelz und Dentin lagen. Jeweils 30 Zähne wurden nach Herstellerangaben mit demselben Füllungsmaterial gefüllt (Prodigy, Silux Plus, Dyract AP, Fuji LC). Anschließend wurden die Restaurationen zunächst mit den gröberen Finierdiamanten und dem Kombifinierer im Rechtslauf konturiert. Jeweils 10 Proben eines jeden Füllungsmaterials wurden mit einem der Instrumente bearbeitet. Auf diese Weise ergaben sich 12 Material-Instrumenten-Kombinationen. Nach dreiwöchiger Wasserlagerung wurde die Rauhigkeit der Füllungsoberflächen mit einem Profilometer gemessen. Außerdem erfolgte eine Auswertung der Randqualität mittels quantitativer Randanalyse. Im Anschluß hieran wurden die Füllungen mit den feineren Diamantinstrumenten bzw. dem Kombifinierer im Linkslauf finiert. Die Füllungen wurden anschließend einer Temperaturwechselbelastung unterzogen (2000 Zyklen zwischen 5°C und 55°C). Erneut erfolgte eine quantitative Randanalyse und eine Oberflächenrauhigkeitsmessung. Die statistische Auswertung der Daten ergab, daß der Kombifinierer im Linkslauf im Gegensatz zu den feinen Diamantfinierern keine Verbesserung der Oberflächenqualität bewirkt. Die Auswirkungen der Instrumente auf die Randqualität ist gleich. Fuji LC weist die höchste Oberflächenrauhigkeit auf. Die übrigen Füllungsmaterialien unterscheiden sich diesbezüglich nicht statistisch signifikant voneinander. Die Silux Plus Restaurationen zeichnen sich durch einen im Vergleich zu den übrigen Materialien hohen Anteil an Randspalten sowohl im Dentin- als auch im Schmelzbereich aus. Die Prodigy Füllungen haben signifikant mehr Randspalten im Dentin als Fuji LC und Dyract AP Füllungen, jedoch auch signifikant weniger als Silux Plus im gleichen Bereich.<br>In this study a newly developed tungsten carbide finishing bur (Brasseler) and conventional coarse and fine grit finishing diamonds of the companies Intensiv and Brasseler were studied with four different filling-materials. The carbide bur is a combination-instrument, that distinguishes itself in the right-hand rotation by a high performance and is intended for the contouring of fillings. When used in a left-hand rotation the instrument should be applied for polishing. In this case the cutting performance is inferior. Oval class-V-cavities (length: 4 mm, width: 3 mm, depth: 2 mm) were prepared into 120 extracted human teeth with one half of the margin length in dentin and one half in enamel. In each case, 30 teeth were filled according to manufacturer-recommendation with the same filling-material (Prodigy, Silux Plus, Dyract AP, Fuji LC). Subsequently the restorations were trimmed with the coarser finishing diamonds and the combination bur with a right-hand rotation. Ten samples of each filling-material were ground with one of the instruments. Thus 12 material-instrument-combinations were established. After three weeks of water-storage, the surface roughness of the fillings was measured with a profilometer. Furthermore, an evaluation of the margin-quality was carried out by means of quantitative margin analysis. After this, the fillings were either polished with the finer diamond-instruments or with the combination-instrument in a left-hand rotation. Afterwards the samples were subjected to a thermocycling procedure (2000 cycles between 5°C and 55°C). Again a quantitative margin analysis and a surface-roughness-measurement were performed. In contrast to the fine diamond instruments, the statistical evaluation of the data revealed that the combination finishing bur does not improve the surface quality in a left-hand rotation. The effect of the instruments on the margin quality is the same. Fuji LC shows the highest surface-roughness, the other filling-materials do not differ statistically significantly from one another. The Silux Plus restorations are characterized by a high percentage of marginal openings in both enamel and dentin. The Prodigy fillings show significantly more marginal gaps in dentin than Fuji LC and Dyract AP fillings, but significantly less than Silux Plus in the same area.
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SOUZA, EDVALDO R. de. "Caracterizações microestruturais e avaliações das propriedades mecânicas das juntas em aço inoxidável AISI 301 L soldadas por MIG e submetidas ao reparo pelo processo TIG." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26797.
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Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-11-11T09:40:30Z
No. of bitstreams: 0<br>Made available in DSpace on 2016-11-11T09:40:30Z (GMT). No. of bitstreams: 0<br>A soldagem tem grande importância no setor metroferroviário, pois é empregada na fabricação de componentes estruturais e no acabamento de vagões de passageiros, que em sua maior parte são de aço inoxidável. As juntas soldadas podem apresentar descontinuidades que são interrupções que afetam as propriedades mecânicas e metalúrgicas da junta soldada. A presença destas descontinuidades, dependendo do seu tamanho, natureza ou efeito combinado, pode ocasionar a reprovação da junta soldada, quer pela redução de propriedades mecânicas ou pela não aceitação, segundo critérios estabelecidos em normas. Uma estrutura que tenha uma solda reprovada durante sua qualificação ou inspeção, pela presença de descontinuidades pode ser recuperada, por meio de um retrabalho a ser realizado nesta junta. A refusão do cordão de solda por meio do processo TIG (Tungsten Inert Gas), sem a utilização do material de adição, é uma técnica de retrabalho que pode ser empregada, em especial pela viabilidade técnica e econômica do processo. Neste estudo analisou-se a influência que o processo de reparo por soldagem TIG exerceu no comportamento mecânico e microestrutural das juntas soldadas pelo processo MIG, por meio de: ensaios mecânicos (tração, fadiga e microdureza Vickers), ensaios não destrutivos (inspeção visual e líquidos penetrantes) e caracterização microestrutural do cordão de solda. Resultados das amostras de ensaio de tração e fadiga indicaram que o reparo dos cordões de solda não alterou o comportamento mecânico das juntas. As juntas submetidas ao reparo nas quais foram retirados os reforços dos cordões apresentaram modificações nas propriedades mecânicas, mas também apresentaram resultados satisfatórios.<br>Dissertação (Mestrado em Tecnologia Nuclear)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Negoita, Cezar Ciprian. "Measurement of neutron flux spectra in a Tungsten Benchmark by neutron foil activation method." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1096547324156-18744.
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The nuclear design of fusion devices such as ITER (International Thermonuclear Experimental Reactor), which is an experimental fusion reactor based on the &quot;tokamak&quot; concept, rely on the results of neutron physical calculations. These depend on the knowledge of the neutron and photon flux spectra which is particularly important because it permits to anticipate the possible answers of the whole structure to phenomena such as nuclear heating, tritium breeding, atomic displacements, radiation shielding, power generation and material activation. The flux spectra can be calculated with transport codes, but validating measurements are also required. An important constituent of structural materials and divertor areas of fusion reactors is tungsten. This thesis deals with the measurement of the neutron fluence and neutron energy spectrum in a tungsten assembly by means of multiple foil neutron activation technique. In order to check and qualify the experimental tools and the codes to be used in the tungsten benchmark experiment, test measurements in the D-T and D-D neutron fields of the neutron generator at Technische Universität Dresden were performed. The characteristics of the D-D and D-T reactions, used to produce monoenergetic neutrons, together with the selection of activation reactions suitable for fusion applications and details of the activation measurements are presented. Corrections related to the neutron irradiation process and those to the sample counting process are discussed, too. The neutron fluence and its energy distribution in a tungsten benchmark, irradiated at the Frascati Neutron Generator with 14 MeV neutrons produced by the T(d, n)4He reaction, are then derived from the measurements of the neutron induced &amp;#947;-ray activity in the foils using the STAYNL unfolding code, based on the linear least-square-errors method, together with the IRDF-90.2 (International Reactor Dosimetry File) cross section library. The differences between the neutron flux spectra measured by means of neutron foil activation and the neutron flux spectra obtained in the same assembly, making use of an NE213 liquid-scintillation spectrometer were studied. The comparison of measured neutron spectra with the spectra calculated with the MCNP-4B (Monte Carlo neutron and photon transport) code, which allows a crucial test of the evaluated nuclear data used in fusion reactor design, is discussed, too. In conclusion, this thesis shows the applicability of the neutron foil activation technique for the measurement of neutron flux spectra inside a thick tungsten assembly irradiated with 14 MeV from a D-T generator<br>Die Konstruktion von Fusionsreaktoren wie ITER (International Thermonuclear Experimental Reactor), der ein experimenteller Fusionsreaktor ist und auf dem &quot;Tokamak&quot;-Konzept beruht, basiert unter neutronenphysikalischen Gesichtspunkten auf den Ergebnissen von umfangreichen Simulationsrechnungen. Diese setzen die Kenntnis der Spektren des Neutronen- und Photonenflusses voraus die besonders wichtig ist, weil sie, die möglichen Antworten der ganzen Struktur auf physikalische Prozesse vorauszuberechnen erlaubt wie z.B.: Heizen durch nukleare Prozesse, Tritium-Brüten, Atomverschiebung, Abschirmung von Strahlung, Leistungserzeugung und Materialaktivierung. Die Flußspektren können mittels Transportcodes berechnet werden, aber es werden auch Messungen zu ihrer Bestätigung benötigt. Ein wichtiger Bestandteil des Strukturmaterials und der Divertor-Flächen der Fusionsreaktoren ist Wolfram. Diese Dissertation behandelt die Messungen der Neutronspektren und ?fluenz in einer Wolfram-Anordnung mittels der Multifolien-Neutronenaktivierungstechnik. Um die anzuwendenden experimentellen Geräte und die Codes, die im Wolfram-Benchmark-Experiment eingesetzt werden, zu überprüfen und zu bestimmen, wurden Testmessungen in den D-T und D-D Neutronenfeldern des Neutronengenerator der Technischen Universität Dresden durchgeführt. Die Eigenschaften der D-T und D-D Reaktionen, die für die Erzeugung von monoenergetischen Neutronen verwendet werden, sowie die Auswahl der Aktivierungsreaktionen, die für Fusionsanwendungen geeignet sind und die Aktivierungsmessung werden detailliert vorgestellt. Korrekturen, die sich auf den Neutronen-Bestrahlungsprozess und auf den Probenzählungsprozess beziehen, werden ebenfalls besprochen. Die Neutronenfluenz und ihre Energieverteilung in einem Wolfram-Benchmark, bestrahlt am Frascati Neutronen Generator mit 14 MeV-Neutronen aus der T(d, n)4He Reaktion, werden aus den Messungen der &amp;#947;-Strahlenaktivität, die von Neutronen in den Folien induziert ist, durch den STAYNL Entfaltungscode, der auf der Methode der kleinsten Fehlerquadrate basiert, zusammen mit der IRDF-90.2 Wirkungsquerschnitt-Bibliothek abgeleitet. Die Unterschiede zwischen den Neutronenflußspektren, die mit Hilfe der Multifolien-Neutronenaktivierung ermittelt wurden, und den Neutronenflußspektren, gemessen im selben Aufbau mit einem NE-213 Flüssigszintillator, wurden untersucht. Die gemessenen Neutronenspektren werden den aus MCNP-4B Rechnungen (Monte Carlo neutron and photon transport) ermittelten Spektren gegenüber gestellt. Der Vergleich stellt einen wichtigen Test der evaluierten Kerndaten für Fusionsreaktorkonzepte dar. Zusammenfassend zeigt diese Arbeit die Anwendbarkeit der Multifolien-Neutronenaktivierungstechnik bei Messungen der Neutronenflussspektren innerhalb eines massiven Wolframblocks bei Bestrahlung mit schnellen Neutronen aus D-T Generatoren
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Thomas, Gareth James. "Advanced materials for plasma facing components in fusion devices." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:f8ba1ae1-f303-4c32-877e-dca421a3cb5c.
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This thesis describes the design, manufacture and characterisation of thick vacuum plasma sprayed tungsten (W) coatings on steel substrates. Fusion is a potentially clean, sustainable, energy source in which nuclear energy is generated via the release of internal energy from nuclei. In order to fuse nuclei the Coulomb barrier must be breached - requiring extreme temperatures or pressures – akin to creating a ‘star in a box’. Tungsten is a promising candidate material for future fusion reactors due to a high sputtering threshold and melting temperature. However, the large coefficient of thermal expansion mismatch with reactor structural steels such as the low activation steel Eurofer’97 is a major manufacturing and in-service problem. A vacuum plasma spraying approach for the manufacture of tungsten and tungsten/steel graded coatings has been developed successfully. The use of graded coatings and highly textured 3D interface surfi-sculpt substrates has been investigated to allow the deposition of thick plasma sprayed tungsten coatings on steel substrates. Finite element models have been developed to understand the residual stresses that develop in W/steel systems and made use of experimental measurements of coating thermal history during manufacture and elastic moduli measured by nano-indentation. For both the graded and surfi-sculpt coating, the models have been used to understand the mechanism of residual stress redistribution and relief in comparison with simple W on steel coatings, particularly by consideration of stored strain energy. In the case of surfi-sculpt W coatings, the patterned substrate gave rise to regular stress concentrating features, and allowed 2mm thick W coatings to be produced reproducibly without delamination. Preliminary through thickness residual stress measurements were compared to model predictions and provided tentative evidence of significant W coating stress relief by regulated coating segmentation.
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Lhuillier, Pierre-Emile. "Etude du comportement de l'hélium et des défauts lacunaires dans le tungstène." Phd thesis, Université d'Orléans, 2010. http://tel.archives-ouvertes.fr/tel-00587482.
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Dans les réacteurs à fusion, le tungstène subira des contraintes sévères dont, l'irradiation neutronique induisant la création de défauts ponctuels, et l'implantation d'hélium. La compréhension du comportement synergique des défauts lacunaires et de l'hélium est cruciale pour modéliser le comportement des composants en tungstène des futurs réacteurs à fusion thermonucléaire.Cette étude utilise la spectroscopie d'annihilation des positons (PAS) pour déterminer la nature et l'évolution en température des défauts d'implantation et l'analyse par réaction nucléaire (NRA)couplée ponctuellement à la microscopie électronique pour suivre le comportement de l'hélium.Les défauts générés dépendent des paramètres d'implantation (nature des ions, énergie, fluence). Par implantation d'3He à 800 keV, des monolacunes ont été créées et sont mobiles entre 473 et 623 K.L'augmentation de la concentration initiale en monolacunes décale le seuil de migration vers les basses températures. Des implantations à fort dpa (Fe 10 MeV) génèrent des amas lacunaires. Les impuretés jouent un rôle prépondérant sur le comportement en température des défauts.Le comportement de l'hélium a été étudié sous trois conditions d'implantation différentes. Les implantations à basse énergie (0,32 keV) montrent la création de complexes hélium-lacune par mutation. Les implantations à 60 keV mettent en évidence la compétition entre la migration, à basse fluence et le piégeage de l'hélium, à haute fluence. Finalement, des implantations à haute énergie(500 keV) renseignent sur l'influence de la microstructure sur la distribution des bulles d'hélium.
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BEN, JDIR MILOUD. "Analyses cristallographiques et chimiques des joints de grains du carbure de tungstene dans le composite wc-co. Etudes en microscopie electronique en transmission." Caen, 1991. http://www.theses.fr/1991CAEN2031.
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L'application des modeles de coincidence a la structure wc du composite wc-co a ete faite avec l'approximation /=1. Les resultats des analyses ont montre qu'unj nombre important de cristaux wc etaient proches d'une relation de coincidence avec un indice de coincidence petit, =2,4,5,7. . . Ces joints de grains peuvent se repartir en trois familles principales: joints de torsion <1010> ou <0001> et joints de flexion <1120>. Dans quelques cas l'analyse en microscopie electronique haute resolution a pu mettre en evidence la structure discrete des dislocations intergranulaires. L'existence de ces dislocations peut etre due soit a une deviation par rapport a l'orientation de coincidence exacte soit au rattrapage parametrique entre a et c. Les segregations de cobalt ont ete detectees dans plusieurs joints de grains. Un nombre important d'analyses a pu ainsi etre effectue et des resultats originaux mis en evidence. Il ne semble pas y avoir de relation simple entre la valeur du rapport de segregation en cobalt et l'indice. Mais la nature cristallographique du plan du joint et la presence de dislocations intergranulaires sont apparues comme deux parametres importants vis-sa-vis de ces phenomenes de segregation. L'etude d'un materiau en carbure de tungstene prepare sans liant cobalt a permis de mettre en evidence des orientations cristallographiques originales par rapport a celles observees dans le materiau composite wc-co
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Plantin, Pascale. "Dépôts multicouches Fe/W sur substrat de Fe par pulvérisation magnétron D. C." Phd thesis, Université d'Orléans, 2006. http://tel.archives-ouvertes.fr/tel-00123902.
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Le masque des tubes cathodiques est un élément déterminant pour la qualité de l'image d'un téléviseur. Le masque est une grille de fer (Fe) oxydée sous forme de magnétite (Fe3O4). Le bombardement électronique subi par le masque génère des gradients de température. Il s'en suit une déformation du masque. L'image perd alors en contraste et en brillance. L'étude a porté sur la détermination, l'élaboration et la caractérisation d'une couche mince limitant ce gradient de température. Le matériau choisi pour cette couche protectrice est le tungstène (W) associé au fer (Fe) sous sa forme oxyde de fer : Fe3O4. Le tungstène est un matériau réfractaire avec un haut coefficient de rétrodiffusion des électrons. De plus, la magnétite possède un bon coefficient d'émissivité thermique. Ces deux propriétés sont essentielles pour éviter la déformation due au gradient de température. L'étude a porté sur les dépôts de couches minces (système bicouche) Fe3O4/W mais aussi alliage Fe-W sur substrat de Fe (matériau du masque). Les dépôts ont été réalisés par pulvérisation magnétron au moyen d'un générateur à décharge continue (pulsée ou non) avec ou sans l'assistance d'un plasma auxiliaire radiofréquence créé par une antenne interne. Pour tenter d'obtenir une couche mince de Fe3O4, nous avons étudié les oxydations ex-situ après dépôts ainsi qu'in-situ pendant ou après dépôts (en les comparant entre elles). Les caractérisations ont concerné l'étude de la structure (microscopie électronique, diffraction des rayons X), l'adhérence (test scotch et diffraction X sous traction), la composition (Spectroscopie de Rétrodiffusion Rutherford et Analyse par Réaction Nucléaire) et la mesure des propriétés optiques infrarouge et thermiques.
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"Desulfurdimerization of dithioacetals with tungsten hexacarbonyl." Chinese University of Hong Kong, 1989. http://library.cuhk.edu.hk/record=b5886174.
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Waterman, Susan Maree. "Some chemistry of tungsten-iridium carbonyl clusters." Phd thesis, 1998. http://hdl.handle.net/1885/144657.
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Pan, Chen-Ling, and 潘貞伶. "The Analysis of Metastable Tungsten Oxide Based Resistance Random Access Memory." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/62808012207447568167.
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碩士<br>國立中正大學<br>物理所<br>95<br>Resistance Random Access Memory (RRAM) has drawn much attention due to its fast access speed like SRAM, high-density storage like DRAM, and the non-volatile property like Flash. Moreover, the structure of RRAM is simple, and the process cost is very low. However, understandings of RRAM materials’ properties and the mechanisms behind resistance switching were still limited. So it is hard to well control the reliability properties and performance in this kind memory.
In our study, RRAM using tungsten oxide (WOx) is tested. The WOx is formed by plasma oxidation of W plugs at low temperature. Tungsten is a metal used in semiconductor industry, so no new material is introduced in RRAM using WOx. The top and bottom electrodes are TiN and W, respectively. The purpose of this study is to investigate the oxidation time on the WOx quality and its electric characteristics.
We found that the slope of lnσ vs. T-1/4 curve and the variable range hopping (VRH) model can give the density of states in localized states after different applied pulse voltages and the active region in VRH model. Moreover, device prepared by longer oxidation time showed small change in the resistance after programming when the pulse voltage was around 0.6~4.6V. This excellent property can provide a very wide operation window for the peripheral circuit design, and this result is very important for future manufacture.
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Wen, Yuh-Sheng, and 聞昱生. "Crystal Structure Analysis of Transition Metal Complexes Containing Silver, Iron and Tungsten." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/42835203326217917994.
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CAI, YI-YOU, and 蔡易佑. "Taguchi Method Analysis With Gas Tungsten Arc Welding of AZ61A Magnesium Alloy." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/85986151835408523918.
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碩士<br>中州科技大學<br>機械與自動化工程系<br>104<br>Advantage of strength to weight ratio, easy forming, heat conduction and magnetic shielding properties widely result in using magnesium alloy for 3C products. In this study, AZ61A Mg-alloy was welded by Tungsten inert gas arc welding (TIG) to investigate the effects of welding parameters on AZ61A Mg-alloy characteristics. Therefore, parts of experiment were conducted with orthogonal arrays of Taguchi method for economically to explore the welding parameters on welding characteristics such as front over melt, end over melt, concave, convex, and crack. Besides, through analysis of variance (ANOVA) and F test of signal to noise (S/N) ratio, the effects of TIG welding parameters such as current type (AC or DC), welding current, welding speed, current efficiency, arc decay time, and shielding gas flow rate on AZ61A weldments characteristics were determined. From this investigation, the relations between AZ61A weldment characteristics and welding parameters of AZ61A via TIG were established. Furthermore, the significant degree of each parameters affected the weldment characteristics were explored, and the optimal combination levels of the welding parameters on front over melt, end over melt, concave, convex, and crack was determined. Moreover, the experimental results could be applied in industrial applications and academic researches.
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Hsieh, Hsieh-Jan, and 謝協展. "Study of Manufacturing Process and Property Analysis of Binderless Tungsten Carbide Material." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/39891786773724436543.
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碩士<br>國立勤益科技大學<br>機械工程系<br>97<br>In this study, binderless tungsten carbide is fabricated under various process parameters, to study the effect of these parameters on mechanical and abrasive properties of the materials. The result of experiment revealed that mechanical properties of the material can be improved by increasing sintering temperature and holding time. However, the hardness of the material degrades with higher sintering temperature as a result of abnormal grain growth. No W2C or other brittle impurity phases are found in XRD or EDS analyses. The optimized set of parameters for gas protected sintering process is a powder diameter of 1.03μm, a sintering temperature of 1860℃ and a holding time of 60 minutes. The relative density of the optimized sample is 95.1%, with a hardness of 1718kg/mm2 and a fracture toughness of 5.97 MPa‧m1/2. Only marginal densification was observed for samples fabricated by 0.63μm powder, because of the conglomeration and sub-microstructure effects of fine power from ball-milling. The result of abrasive tests indicated that the volume wear rate is 3.68x10-5cm3/g for optimized samples, and is 6.76x10-5cm3/g for traditional alloy (P10); the fabricated samples are nearly twice wear resistant than traditional alloys.
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蔡侑東. "Fabrication and analysis of solid-state tungsten trioxide－nickle oxide complementary electrochromic devices." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/40327053280968176982.
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Zhao, Qing-huang, and 趙清煌. "The Parametric Analysis in Fabrication of Tungsten Carbide Alloy Rod by Electrochemical Machining." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/33298594800715427170.
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碩士<br>國立中央大學<br>機械工程學系<br>104<br>Electrochemical machining (ECM) is one of the non-traditional manufacturing process, shaping workpiece by electrolysis. The advantages are that the process is independent of material properties, little or no tool wearing, no surface stress, and good surface finishing. The machining equipment is relatively simple and inexpensive with fast processing speed, and capable of complex workpiece geometry.
Tungsten carbide (WC) alloy has high stiffness and high surface hardness, commonly used in cutting tools and mold. But in ECM, passivation layer will be generated in sodium nitrate (NaNO3) electrolyte, and significantly reduce the material removal rate (MRR) in anode. The object of this study was to take sodium nitrate and ammonia hydroxide (NH4OH) as hybrid electrolyte in ECM process, and investigate the effects of various processing parameters (e.g. applied voltage, NaNO3 concentration, NH4OH concentration, electrode rotation speed, and machining time) on MRR and electrode shape.
The results show that, with condition of 20 V, 4 M NH4OH and 3000 rpm, there will be largest MRR. Meanwhile, the shape of electrode will be tapered if NaNO3 is 2 M, and reversely tapered with uneven surface if NaNO3 is 4 M. Surface quality will slightly degrade after machining. Machining time can control MRR rather than electrode shape.
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SHEN, BAI-CHENG, and 沈柏承. "Analysis and Optimization of Optical Projection Grinding for the WF30 Tungsten Steel Punch." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/q9tkmk.
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碩士<br>修平科技大學<br>精密機械與製造科技碩士班<br>107<br>The tungsten steel punch used in precision molds requires high dimensional accuracy and needs to be achieved by optical projection grinding. In this study, the optical projection polishing process was used to process the dimensions and surface of the WF30 tungsten steel punch. The grinding feed rate, grinding depth, head swing rate, and type of grinding wheel were used as processing parameters to observe the processing characteristics, such as dimensional accuracy, surface quality and surface texture. The response surface method (RSM) is used to generate a second-order mathematical module, thereby explaining the interaction between the optical projection grinding parameters and processing quality characteristics. The results show that using the lower grinding feed rate and the lower grinding depth combined with a low head yaw rate, the good surface quality and the dimensional accuracy of the workpiece can be obtained. Grinding using the grinding wheel type #800 will result in better surface quality of the workpiece.
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Liao, Tsu-Wei, та 廖梓為. "Single crystal growth and structure analysis of hexagonal tungsten bronzes in superconducting Rb0.23WO3+δ". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/97246635678924299659.
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碩士<br>淡江大學<br>物理學系碩士班<br>95<br>Rubidium tungsten bronze RbxWOy (0.19< x< 0.33,2.9< y< 3.05) has been observed that the oxygen concentration dependent metal-nonmetal transition, and the rubidium and oxygen concentration dependent distribution for superconductivity critical temperature. In order to investigate the properties of RbxWOy more clearly, the preparation for single crystalline samples Rb0.23WOy (2.90≦y≦3.00) was carried out. The melting point of Rb0.23WOy increases as the oxygen concentration decreases. The melting point of Rb0.23WO3.00 is 1190oC and that of Rb0.23WO2.90 is 1210oC. And the size of single crystals affected by the cooling rate of calcination. The back-reflection Laue method presents p2mm symmetry along (1 0 0), and p6mm symmetry along (0 0 1) respectively for all single crystals with different oxygen concentration. The single crystalline Rb0.23WO3.00 was annealed in oxygen, and the superconductivity was observed above 3 K while the original material didn''t superconduct above 2 K, and the lattice parameter c decreased as the annealing times increased.
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Chung, Lin-Shu, and 鍾林樹. "The planning and analysis of grinding process for end-mill of cemented tungsten carbide." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/p6sy79.
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碩士<br>國立虎尾科技大學<br>動力機械工程研究所<br>94<br>Because the cutting method promotes much today, the high precision tool was extremely demanded in the cutting field. The tool shape, accuracy, and cutting performance depend much on the tool grinding process. Due to the limited properties of traditional tool grinding machine, some accessories must be assembled in the machine and operated it by steps. That made a low precision tool and poor tool cutting performance. Moreover, the non-consistent and the non-common in the grinding process made it impossible to construct a standard grinding process. By the constructed model and documents, a full cycle for grinding a precision tool could be got on the CNC tool grinding machine.
The main purpose of this paper was to grind a high precision tool by tool grinding CAM system and an analysis of grinding performance on a 5-axis CNC tool grinder machine made by Topwork. The basic grinding process planning and analysis for tool grinding included: grinding methods, tool geometry, sequence displacement of approach and retract in each axis, surface roughness of relief face, tool geometry angles of tool, and the grinding parameters.
In grinding a high precision tool, suitable wheels and wheel setting for grinding process should be chosen first which was based on the tool size. Then the CAM system of tool grinding will be applied for setting the appropriate parameters and find the optimal amount and sequence of approach and retract of wheel. Finally, simulated the 3D motion of tool and machine in the software, a safety cutting path could be gotten and a precision tool could be produced.
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蔡孟霖. "Optimization analysis for gas tungsten flux-cored arc welding procedures with duplex stainless steel plate." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/96621712320281680045.
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碩士<br>國立高雄應用科技大學<br>機械工程系<br>105<br>ABSTRACT
In this paper, the use of duplex stainless steel plate, according to regulations to develop welding procedures, through the Taguchi method and the reaction surface design welding parameters, Use gas tungsten flux-cored arc welding, The tensile strength data were obtained by mechanical universal testing machine, And then use the Taguchi method and the reaction surface method to obtain the optimization parameters. In the future, this research method will be applied to practical welding and welding of all kinds of materials to improve efficiency, quality, reduce cost and time.
In the research and analysis process using the same kind of metal material, through the Taguchi method and the reaction surface method to design different welding current, welding voltage, welding speed, shielding gas and other related parameters, the double-phase steel plate test piece welding. After the test piece was processed, the tensile strength data were tested by the mechanical universal testing machine, and the data were re - introduced into Taguchi method and the reaction surface method to find the optimization parameters.
The design uses the Taguchi method to direct the table L9 (34), After welding and data collection and analysis, the welding current A3 (250A), welding voltage B3 (35V), welding speed C3 (45cm / min.), Gas flow D2 (20l / min.), After verification of the tensile strength of 821.6 N / mm2, Surface design using Box-Behnken design of three leveling factors: welding into the heat (A), welding speed (B), gas flow (C), After analysis, the significance of factor A and C was less than 0.05, Factor B has no obvious relationship, the results show that the residual difference is relatively small, So it can be a single target surface reaction method of the best analysis, The results are as follows: into the heat 7890W (A), welding speed 45cm / min. (B), gas flow 15 l / min., Verify the tensile strength of 826.7 N / mm2.
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Liu, Hsin-Tzu, and 劉歆慈. "Analysis and Study on the Properties of High Purity Tungsten Prepared by Electron Beam Melting." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/y366mf.
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碩士<br>國立臺北科技大學<br>材料科學與工程研究所<br>105<br>The melting point of tungsten is the highest in nature, and tungsten has high density, high strength and superior corrosion resistance. So it’s widely used in medical, electronic steel metallurgy and other industries, and high-purity tungsten target is one of the basic materials for the production of integrated circuits. Therefore, how to develop a production of high purity tungsten metal material metallurgical smelting technology is very important. In this study, two melting experiments were carried out by electron beam smelting, and the crystal structure was observed by XRD. The crystal plane of tungsten ingot was mainly (110) plane after long refining. The elemental content was analyzed by inductively coupled plasma mass spectrometry (ICP-MS) with an optimum purity of 7N7. From the metallographic analysis, the average grain area of the tungsten ingot is about 0.554 cm2. From the TEM, the lattice constants of the two ingots were 0.3366 nm and 0.3441 nm, respectively, which were close to the theoretical values.
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Archer, Marcelle. "Analysis of cobalt, tantalum, titanium, vanadium and chromium in tungsten carbide by inductively coupled plasma - optical emission spectrometry." Diss., 2004. http://hdl.handle.net/2263/24896.
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CHAO, CHIH-LUNG, and 趙芝龍. "Ti-15V-3Cr-3Sn-3Al Alloy in Electron Beam and Tungsten Inert Gas Arc Welding Produce Microtexture and Mechanical Property Analysis." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/86168697449053485408.
Full textAbstract:
碩士<br>國防大學中正理工學院<br>兵器系統工程研究所<br>94<br>Considering that the Ti-6A1-4V alloy widely used by the industrial field is insufficient for molding work, a series of mechanical properties and microstructure analysis was conducted in this research for the Ti-15V-3Cr-3Sn-3Al, which presents satisfactory molding performance. Firstly, the effect of heat treatment under varied cooling rates on the relevant mechanical properties and microstructure are studied. Secondly, the material butt-welding are performed by EBW and the TIG welding method respectively to further study the effect of heat-treatment process before and after the welding together with the microstructure and mechanical property investigation of the welded sample. Therefore, the optimal heat treatment parameters can be obtained by the above test results.
The result of the heat-treatment conducted under varied cooling rates shows that, when putting under S.T.+F.C.+A.A. heat treatment conditions, enhanced tensile strength could be obtained while still having good elongation. The result of the Butt-welding also indicated that the pre-welding heat treatment would not bring a visible effect to the mechanical properties. However, the needle-type -phase precipitate from grain interior through the post-welding heat treatment can enhance the hardness and strength of the welding subject at the expense of elongation reduction.
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WU, JUNG-TSAN, and 吳榮燦. "Research on the Analysis of Industrial Management Strategy of Tungsten Steel Milling Cutter—Taking Yuanjun International Co., Ltd. as an Example." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/up4mx6.
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碩士<br>東海大學<br>高階經營管理碩士在職專班<br>107<br>This study is based on the case study of Yuanjun International (shares) company located in Taichung Industrial Zone (herein after referred to as the case company) to explore the company's business development strategy. The case company is Taiwan's top ten machine tool cutter manufacturers with 23 years of operating experience. The research methods mainly include case company visits and implementation of questionnaire surveys. The main research and analysis found that although Taiwan has abundant human resources and good geography, but it faces technical problems where talents are not easy to cultivate, mainland natural resources limit exports, and Taiwan's raw materials have no advantages. By determining the success or failure through the details, Taiwanese companies must pay attention to refined management, strict management of production processes, and strive for excellence so that the quality of their products is stable and can be continuously improved. Taiwanese companies must also strive to upgrade their technology and develop new low-cost, high-precision and custom-made products. From the analysis of the external environment, it is found that the potential competitors have low threats, medium bargaining power to suppliers, high bargaining power to customers, no threat of substitutes, and high intensity of competition within the industry.
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Wu, Yu-Ru, and 吳育儒. "The Analysis of Cutting Performance in the Plastic Materials for the Grinding Precision and the Cobalt Content of Tungsten Carbide of End Mills." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/382a75.
Full textAbstract:
碩士<br>國立虎尾科技大學<br>機械與電腦輔助工程系碩士班<br>104<br>Since the plastic material itself has good toughness, so when cutting plastic materials, in the past are adjusted for tool geometry or machining parameters, thereby reach to enhance tool life, but with the advances in technology, in addition to the plastic composite material increase their own strength plastic material, the plastic material of the cutting cutting more difficult, but now in terms of cutting the plastic rarely for precision grinding tools and tungsten carbide cobalt content to explore research, so this study end precision grinding and milling of tungsten carbide cutting analysis of cobalt content on the plastic material.
In this study, the impact tool edge precision grinding process parameters were cutting surface grit size, cutting surface feed rate, cutting surface speed, relief surface grit size, relief surface feed rate and the relief surface speed, use Taguchi experiment Planning Act, the analysis of L36 (22 × 34) orthogonal table to find the best, the worst and moderate three levels of precision grinding, precision grinding and then in accordance with each grinding tungsten carbide rods with different cobalt content, total available nine different tool characteristics to a series of cutting analysis.
The experimental analysis showed that cutting blue PC material (EXL14414) to the tool component cobalt content of 8% of its edge polishing accuracy 1.095μm has better tool life quality; cutting white material PC (EXRL2031) to the tool component cobalt content 8% of its edge polishing accuracy 1.095μm has better tool life quality; cutting black PC glass material (Kalix 9950) to the tool component cobalt content of 9% of its accuracy 1.095μm edge grinding tool life with better quality.
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葉元勳. "A Study on the Application of the Taguchi Method and the Grey Relational Analysis in the Gas Tungsten Arc Welding of AISI316 Stainless Steel." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/73727269734310110700.
Full textAbstract:
碩士<br>國立臺灣師範大學<br>工業教育學系<br>94<br>The purpose of this study was to obtain the optimal welding process parameters in experimental range by the taguchi method with the grey relational analysis. The correlated results and discussions were focused on multiple quality characteristics as weld microhardness, weld width, and weld undercut.
In experiments, the gas tungsten arc welding was used. The base metal were the sheets of type 316 stainless steel . The welding method was butt welding with filler by a servo mechanism. In the experimental design, a L18 orthogonal array was used to reduce the number of welding experiments and the selection of process parameters inclueded the arc length, welding current, welding speed, root openings, filler speed and nitrogen content in shelding gas.
In the single quality characteristic, the experimental result showed that the average of weld microhardness was Hv194.2 for the optimal process parameter and Hv178.8 for the initial process parameter. The hardness was arised about 9%. The average of weld width was 7.88mm for the optimal process parameter and 10.15mm for the initial process parameter. The width was decreased in 2.27mm. The weld of the optimal process parameter indicated no undercut. The weld of the initial process parameter indicated serious undercut.
In the optimal process parameter of multiple quality characteristics, the experimental result showed that the average of weld microhardness was Hv178.5, the average of weld width was 8.23mm and the weld was no undercut. All of the optimal process parameters had good reproducibilities which were less than 30%.
When the shilding gas was pure argon, the microstructure of weld showed ferritic-austenitic morphology. When the nitrogen content in the shelding gas was 1%, the microstructure of weld showed ferritic-austenitic morphology but the ferrites were semicontinous. When the nitrogen content in the shelding gas was 2%, the microstructure of weld showed the mixture of ferritic-austenitic morph-
ology and austenitic-ferritic morphology.
In the further, there is an following advice of reserch : It is possible to design a curve by applying dynamic characteristics in the taguchi method. To do this, we can reach the goal of optimal process welding parameter just change signal factros. It is worth to make efforts on this probem.
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Yeh, Po-Cheng, and 葉柏成. "Modeling and analysis of surface roughness and electrode wear on the wire electrical discharge machining of cobalt-bonded tungsten carbide using the response surface methodology." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/92352988685852175596.
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碩士<br>修平技術學院<br>精密機械與製造科技研究所<br>97<br>In this paper, the predictive model of surface roughness (SR) and wire-electrode wear (WW) in the Wire Electrical Discharge Machining (WEDM) process of cemented tungsten carbide using the response surface methodology had been carried out. The cemented tungsten carbide P10 grade, which is widely used in mould and tool applications, was adopted as the workpiece material to explore the performance characteristics of WEDM process. The first and second order models were developed to study the effect of four processing parameters, pulse duration, open discharge voltage, peak current and wire speed on the surface roughness (SR) and wire-electrode wear (WW). The experiment plan adopts the centered composite design (CCD). The predictive models proposed in this study were investigated by the analysis of variance (ANOVA). The second order model in this study have been proved to fit and predict values of the performance characteristics close to those readings recorded experimentally with a 95% confidence interval.
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Souto, Ana Sofia de Sousa Glória e. Valadares. "SEDEX heritage in tungsten-gold skarn deposits of Serra de Arga metamorphic suite: structural and paragenetical analysis of sulfide-rich calc-silicate rocks and its mineralizations." Master's thesis, 2019. http://hdl.handle.net/1822/65484.
Full textAbstract:
Dissertação de mestrado em Geosciences (área de especialização em Valorisation of Geological Resources)<br>In the sequence of a structural and geochemical study about the SEDEX to volcanic affiliation of
some metamorphic units of Serra de Arga (Northern Portugal), attention was drawn towards Covas dome,
located in the Silurian terrains of Serra de Arga. A prior geochemical data set for the meta-volcanic rocks
suggests a transitional signature between mantle source alkali basalts and transitional-tholeiitic to
transitional-calcalkaline magmatic series. The primitive genesis and emplacement of those rocks as well
as some contemporary vanadium-rich exhalative facies are consistent with back-arc anoxic basin systems,
precursor to rifting onset (Dias, 2011). At Cerdeirinha mine, one of the ore deposits of Covas Dome,
tungsten mineralization, although remobilized by metassomatism, might be considered partially related
to Silurian volcanic activity. Apparently in the main front of Cerdeirinha open pit, previously to the calcsilicate
paragenesis of metasomatic type there would be structural devices and relics of syngenetic
signatures of the SEDEX-type (Leal Gomes et al., 2011).
The present study was focused mainly in the structures of the deposit, its survey and detailed
analysis especially of the main clearing front of the open pit. Also, paragenetic analysis, E.P.M.A., and
L.A.-I.C.P.-M.S. measurements were executed.
In what regional metamorphism and ore geothermmobarometry concerns, hornblendeplagioclase
intergrowth, chlorites and arsenopyrite were analysed.
L.A.-I.C.P.-M.S. pyrite compositions are not clearly conclusive, but could be related with only
sedimentary-exhalative setting or with a SEDEX signature overprinted due to hydrothermal alteration,
adding up with some skarn-like assemblages. Contents of REE scheelite and apatite suggest a fluid
fractionation and an order of crystallization sequenced from central to periphery of the rock exposures at
the open pit domain.
A Mn-rich indetermination was found, possibly related with a primordial submarine Mn-rich
exhalation. This study did not found a clear and strict evidence of a protolithic SEDEX setting, however it
shows some indications of this type of pristine depositions that must be thought of in future studies.<br>Subsequentemente ao estudo estrutural e geoquímico de assinatura vulcanogénica a exalativa de
algumas unidades metamórficas da Serra de Arga (Norte de Portugal), atenção centrou-se no Domo de Covas,
estrutura localizada nos terrenos silúricos da Serra de Arga. A génese das rochas primitivas, e de algumas
fácies exalativas enriquecidas em vanádio, são consistentes com os sistemas de bacias anóxicas de retro-arc,
precursoras do início do rifting (Dias, 2011). Na mina da Cerdeirinha, um dos jazigos do Domo de Covas, a
mineralização de tungsténio, embora remobilizada pelo metassomatismo, pode ser considerada parcialmente
relacionada com a atividade vulcânica silúrica. Aparentemente, na frente principal da mina a céu aberto da
Cerdeirinha, anteriormente à paragénese calcossilicatada do tipo metassomática, existiriam dispositivos
estruturais e relíquias de assinaturas singenéticas do tipo SEDEX (Leal Gomes et al., 2011).
O presente estudo teve como foco principal as estruturas do depósito, levantamento e análise
detalhada, principalmente da principal frente de mina a céu aberto. Além disso, a análise paragenética, e
medições de E.P.M.A. e L.A.-I.C.P.-M.S. foram executadas.
No que respeita à geotermobarometria de metamorfismo regional e minério foram analisados o
intercrescimento hornblenda-plagioclase, clorites e arsenopirites.
Relativamente às medições de pirite através de L.A.-I.C.P.-M.S., estas não são claramente
conclusivas, contudo podem estar relacionadas apenas com a hipótese sedimentar-exalativa ou com uma
assinatura SEDEX sobreposta pela alteração hidrotermal, que terá originado associações mineralógicas típicas
de skarn. Os conteúdos de terras raras da scheelite e apatite sugerem o fracionamento do fluído e uma ordem
de cristalização do centro para a periferia rochosa na frente de mina.
Foi encontrada uma indeterminação enriquecida em Mn, possivelmente relacionada a exalações
primordiais ricas em Mn. Este estudo não encontrou uma evidência clara e estrita de uma configuração
protolítica SEDEX, contudo mostra algumas indicações deste tipo de deposição pristina, que deve ser pensada
em estudos futuros.