Добірка наукової літератури з теми "Tunsten"

Polyaniline/tungsten carbide (PANI/WC) composite was synthesized by chemical oxidative polymerization of aniline using ammonium persulfate as the oxidant and thermal treated in air at 150°C, 250°C, 350°C and 450°C to 2 hours. The changes of structure, crystalline and conductivity were investigated by Fourier Transformed Infrared (FT-IR), Fourier Transformed Raman (FT-Raman), X-Ray Diffraction (XRD) and four-probe technique. The results showed that PANI/WC composite showed much-improved thermal stability compared to pure PANI. But the conductivity of PANI/WC is reduced to some extent (1.73 S/cm, the conductivity is reduced by about 82%) after thermal treated at 250°C, and dropped by 6 orders of magnitude (3.25×10-6S/cm) at 350°C. This may be explained by that only a fraction of dopant losses during thermal treatment at 250°C, but after thermal treatment at 350°C, along with cross-linking, chain scission and oxygen, resulting in destruction of crystal structure, decrease of the emeraldine sequence.

In the application of welding "GTAW" has several advantages such as welding results do not need to be cleaned from slag or corrosion residue. Due to the above-mentioned advantages, the precise determination of weld parameters and offset by the welding skills of welded characteristics will be affected. The purpose of this research is to know the characteristic of GTAW welding on low carbon steel, by observing the shape of weld bead and supported by the result of macro photo of welding result from various variations of currents and variations of the angle geometry of tungsten electrode. The method used in this study is an experimental method, with treatment of parameters of parameters of current and parameters of angle geometry variation of tapering of tunsten electrode. Analyze method is done to welding result and macro photo of T connection weld result. From the analysis of GTAW weld metal form with type T connection through variation of electrode geometry angle and strong welding current in this research, can be drawn some conclusions, among others, from some variation of weld geometry angle which gives good shape of welding characteristic and deep penetration is angle 300 of ampere 90 A.

ISRO space programs use Maraging Steel for its Solid rocket motor casings. Because of its higher cost and limitations in the availability,there is a need to develop alternate to this steel.ISRO has developed a unique material as a alternative to Maraging Steel namely 0.3%C-Cr-Mo-V steel (Electro Slag Refined modified 15CDV6 steel-ESR MOD 15CDV6). This material is being considered for making rocket motor casings and considered as substitute as well as replacement for Maraging Steel.Weldability is an important factor considered for fabrication of this material in the areas of rocketry.Since it is a new material, enough studies and welding details are not available to exploit this material for aero space applications.Among the various welding methods available in the welding of steels,GTAW (Gas Tunsten Arc Welding) process selected for undertaking this study because this process is clean,contamination free, easily adaptable and generally suitable for welding of high strength alloy steel.Literature survey indicates not much work has been reported in welding of such low alloy high strength steel with conventional welding methods.Similarly effect of heat treatment on weldments,quench characteristics,hardness response etc.also not available much. Hence, these factors are main reason to undertake this study.This paper is limited to studying , fixing of weld parameters and weld bead dimensions. In this expriment the welding parameters , its response for each set of experiments and influence on weld dimensions are studied.In this work a combination of weld parameters were selected using Design of Experiment (DOE) principle with three levels and four parameter (variables).Totally nine experiments with different combination of parameters conducted on the test coupons of size 8×200×150mm.The chemistry of parent metal and filler rod remains same. Three levels of current and voltage,and correspondingly other parameters like root gap,number of passes and welding speeds were employed.Details like the amount of shielding, purging gas used and quantity of flow are noted.Weld bead dimensions like bead width –B,reinforcement-R,penetration –r,penetration height-b are chosen as response.All the nine test coupons were subjected to Liquid Penetrant Test (LPT), X-ray radiography and found defect free.

Lollardy, the native English heresy vigorously suppressed since the early fifteenth-century, did not die with its suppression in the wake of the rebellion of Sir John Oldcastle in 1414. A century later Lollard beliefs remained current, albeit in varied forms. The most consistent features in this eclectic religious system were the possession and reading of English translations of the Scriptures, a sacramentarian view of the Eucharist, and an often vehement anticlericalism. With few exceptions Lollardy was the preserve of the unlearned; based on the religious fringes of towns and the greater cities, rather than in the learned centers of the universities or the Court.

AbstractJames Tunstead Burtchaell had been teaching Rosemary Haughton's 1967 book The Transformation of Man for a number of years when he published Philemon's Problem in 1973. Now, with both authors having reworked their books in the last two years, we are given an opportunity to compare and contrast the development of Burtchaell's and Haughton's thinking on how grace transforms human beings. The present essay sees an intellectual convergence between Haughton and Burtchaell; it sees much to be grateful for in both books by both authors; and it claims that Haughton's new book has developed her thinking on grace's communal character further than Burtchaell's new book has developed his thinking on the same topic.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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A busca por novas fontes renováveis de energia tem se tornado de grande apelo devido à necessidade de se reduzir os impactos ambientais. Esse interesse tem motivado a pesquisa e o desenvolvimento de células fotovoltaicas (CFs) mais eficientes e baratas. Assim, a energia solar fotovoltaica tem sido uma opção para se complementar e ampliar a geração de eletricidade. Entretanto, as células de silício cristalino (Si-c) disponíveis no mercado apresentam baixa eficiência de conversão da radiação luminosa em energia elétrica devida, principalmente, às perdas por incompatibilidade espectral entre as regiões de máxima emissão solar (região do visível - Vis) e de máxima eficiência fotovoltaica da célula de Si-c (região do infravermelho - IV). Para minimizar essas perdas e, consequentemente, melhorar a eficiência da CF, conversores descendentes de energia compostos por íons terras-raras são usados na conversão de fótons de alta energia (Vis) em fótons de menor energia (IV). Nesse ínterim, no presente trabalho foram estudadas as propriedades espectroscópicas dos íons neodímio (Nd3+) e itérbio (Yb3+) incorporados, como dopantes, no vidro telurito-tungstênio (TW). Tais propriedades foram obtidas a partir de medidas de difração de raios-X, densidade de massa, espectroscopia de infravermelho por transformada de Fourier, Raman, absorção óptica, luminescência, excitação, evolução temporal da luminescência e lente térmica. Este estudo foi dividido em duas etapas. Primeiramente, vidros TW dopados com Nd3+ foram preparados em diferentes atmosferas, i.e., uma atmosfera ambiente e outra rica em O2, para investigação da influência dos grupos hidroxilas (OH) nas propriedades espectroscópicas de amostras com diferentes concentrações de Nd3+. A dependência com a concentração indicou que a transferência de energia do íon Nd3+ para o grupo OH foi desprezível e que a eficiência quântica luminescente do nível 4F3/2 diminuiu com o aumento da concentração de Nd3+. Posteriormente, vidros TW co-dopados com Nd3+ e Yb3+ foram preparados em atmosfera ambiente para investigação da correlação entre os íons Yb3+ e os mecanismos de conversão descendente de energia (CDE). Os resultados mostraram que a luminescência, oriunda do nível 4F3/2, diminuiu com o aumento da concentração de íons Yb3+. Simultaneamente, observou-se um aumento correspondente na emissão do Yb3+ e uma redução no calor gerado pela amostra. A transferência de energia Nd3+ → Yb3+ foi observada qualitativamente e a eficiência dessa transferência foi avaliada quantitativamente por valores do tempo de vida. Esses resultados indicam que o vidro TW co-dopado com íons Nd3+ e Yb3+ é um sistema com potencial para ser usado como material conversor descendente de energia aplicado sobre as células fotovoltaicas de Si-c.
The demand for new and renewable energy sources has been of great appeal due to the reduction of environmental impacts. This interest has motivated the research and the development of more efficient and less expensive photovoltaic (PV) cells. Thus, the photovoltaic solar energy has been an option to complement and expand the generation of electricity. However, commercialized crystalline silicon cells present low conversion efficiency of the light irradiation energy into electric energy, mainly due to the spectral mismatch between the regions of maximum solar emission (visible spectrum) and of maximum PV cell efficiency, which is in infrared region. To minimize such losses and, consequently, improve the efficiency of PV cell, down-converters with rare-earth ions in their structure are used to convert the high energy photons (at the visible - Vis) into low energy photons (at the infrared - IR). Meanwhile, in the present work we study the spectroscopic properties of neodymium (Nd3+) and ytterbium (Yb3+) ions incorporated as dopants in a tellurite-tungsten (TW) glass matrix. The characterization of the samples were obtained from measurements of X-ray diffraction, mass density, Fourier transform infrared spectroscopy, Raman spectroscopy, optical absorption, luminescence, excitation, temporal evolution of the luminescence and thermal lens. This study was divided into two stages. Primarily, Nd3+-doped TW glasses were prepared in different atmospheres, i.e., an ambient atmosphere and in another rich in O2 to investigate the influence of the hydroxyl (OH) groups in the spectroscopic properties of samples with different concentrations of Nd3+. The results showed that the energy transfer from Nd3+ ion to the OH group was negligible. The concentration dependency indicated that the energy transference from the Nd3+ ion to the OH group was negligible. In addition, the luminescent quantum efficiency of 4F3/2 level decreased with increasing of Nd3+ concentration. Subsequently, Nd3+ and Yb3+ co-doped TW glasses were prepared in ambient atmosphere to investigate the correlation between Yb3+ ions and down-conversion (DC) mechanisms. The results showed that the luminescence of the 4F3/2 decreased as the concentration of Yb3+ was increased. Simultaneously, it was observed a corresponding increase in the emission of the Yb3+ and a reduction in the generated heat by the sample. The Nd3+ → Yb3+ energy transfer was observed qualitatively and the efficiency of such transfer was quantitatively evaluated by lifetime values. The results indicate that the co-doped TW glasses by Nd3+ and Yb3+ are systems with potential to be used as down-converter material applied to the c-Si photovoltaics cells.

Orientador: João Carlos Silos Moraes
Abstract: The demand for new and renewable energy sources has been of great appeal due to the reduction of environmental impacts. This interest has motivated the research and the development of more efficient and less expensive photovoltaic (PV) cells. Thus, the photovoltaic solar energy has been an option to complement and expand the generation of electricity. However, commercialized crystalline silicon cells present low conversion efficiency of the light irradiation energy into electric energy, mainly due to the spectral mismatch between the regions of maximum solar emission (visible spectrum) and of maximum PV cell efficiency, which is in infrared region. To minimize such losses and, consequently, improve the efficiency of PV cell, down-converters with rare-earth ions in their structure are used to convert the high energy photons (at the visible - Vis) into low energy photons (at the infrared - IR). Meanwhile, in the present work we study the spectroscopic properties of neodymium (Nd3+) and ytterbium (Yb3+) ions incorporated as dopants in a tellurite-tungsten (TW) glass matrix. The characterization of the samples were obtained from measurements of X-ray diffraction, mass density, Fourier transform infrared spectroscopy, Raman spectroscopy, optical absorption, luminescence, excitation, temporal evolution of the luminescence and thermal lens. This study was divided into two stages. Primarily, Nd3+-doped TW glasses were prepared in different atmospheres, i.e., an ambient atmosphere and... (Complete abstract click electronic access below)
Resumo: A busca por novas fontes renováveis de energia tem se tornado de grande apelo devido à necessidade de se reduzir os impactos ambientais. Esse interesse tem motivado a pesquisa e o desenvolvimento de células fotovoltaicas (CFs) mais eficientes e baratas. Assim, a energia solar fotovoltaica tem sido uma opção para se complementar e ampliar a geração de eletricidade. Entretanto, as células de silício cristalino (Si-c) disponíveis no mercado apresentam baixa eficiência de conversão da radiação luminosa em energia elétrica devida, principalmente, às perdas por incompatibilidade espectral entre as regiões de máxima emissão solar (região do visível - Vis) e de máxima eficiência fotovoltaica da célula de Si-c (região do infravermelho - IV). Para minimizar essas perdas e, consequentemente, melhorar a eficiência da CF, conversores descendentes de energia compostos por íons terras-raras são usados na conversão de fótons de alta energia (Vis) em fótons de menor energia (IV). Nesse ínterim, no presente trabalho foram estudadas as propriedades espectroscópicas dos íons neodímio (Nd3+) e itérbio (Yb3+) incorporados, como dopantes, no vidro telurito-tungstênio (TW). Tais propriedades foram obtidas a partir de medidas de difração de raios-X, densidade de massa, espectroscopia de infravermelho por transformada de Fourier, Raman, absorção óptica, luminescência, excitação, evolução temporal da luminescência e lente térmica. Este estudo foi dividido em duas etapas. Primeiramente, vidros TW dopado... (Resumo completo, clicar acesso eletrônico abaixo)
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The Mt. Carbine tungsten deposit represents a good example of granite related sheeted vein mineralization recording the late stages of granite cooling volatile differentiation and subsequent expulsion. The presence of 3 distinct mineralizing stages has been recognized through the study of the alteration and mineral paragenesis. These observations coupled with geochemical analysis have culminated in unraveling some of the physiochemical conditions under which the deposit formed and their dynamic evolution through time. Along with gaining important insights into the formation of the deposit analyses were conducted on individual minerals from different parts of the deposit as an investigation into their possible use as geochemical vectors to mineralization through trends in trace and REE chemistry. The findings of the study indicate that the deposit formed as a result of fluid expulsions from a single magmatic event forming a distinctive high to low temperature and reduced to oxidized fluid evolution. The study also found the presence of 2 distinct alteration assemblages which although containing some lithologically induced heterogeneities appear as a alkaline distal and potassic proximal alteration. The use of mineral geochemistry as an exploration tool in many of the tested cases has proven to either be of little potential use whereas others have not been tested adequately. Wolframite Fe/Mn ratios have proven as being potentially useful as a means of delineating vertical displacement from the source of the mineralizing fluids due to the telescoped nature of the vein fill minerals.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2011

Sustainable fusion power is within reach; however, more research is needed in the field of material science and engineering. One critical component of a fusion reactor is the plasma facing material. Very little literature exists on the sustainability of tungsten as a plasma facing material (PFM). During operation, PFM must withstand harsh conditions with combined effects from high temperature, mechanical stress, irradiation, transmutation, and the production of hydrogen (H) and helium (He) from nuclear reactions. Therefore, this thesis will focus on co-implantation of H and He into tungsten to investigate the mechanical and microstructural material response. For the first part of this study, Molecular Dynamics (MD) was used to qualitatively understand defect migration and mechanical property changes in tungsten. A Brinell hardness test was simulated using MD in tungsten to study the dependence on void size and void density hardness. It was found that hardness changes vary as the square root of the void size and void density. Also the movement of dislocations and its interaction with voids were investigated. For the second part of the study, H and He were co-implanted into tungsten to look at the mechanical and microstructural changes. Hardness changes were measured using a nano-indenter ex-situ on post-irradiated specimen. Results show that the hardness of tungsten after co-implantation is proportional to the square root of the fluence. Additionally, the microstructure of irradiated tungsten samples was investigated by using a Transmission Electron Microscope (TEM). It was observed that the defect microstructure in tungsten, after co-implantation, is quite complex, with a number of intriguing features, such as the presence of the nano-bubbles and dislocation loops. Also it was observed that there was an effect that H has on the nucleation of He nano-bubbles. The results from this work suggest that the effect of co-implanting H and He into tungsten is crucial to fully understand its viability as a PFM.

Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e Tecnologia
Este estudo enquadra-se no âmbito da inovação e melhoria contínua de uma área empresarial muito concreta, a indústria das ferramentas de corte. O foco central é o desenvolvimento e percepção da relação entre o estado de tensões introduzido numa ferramenta de corte e a melhoria ou não das suas propriedades mecânicas e tribológicas com o mesmo. As pastilhas de corte estudadas são constituidas por carboneto de tungsténio com cobalto, ou seja, trata-se de um material cerâmico com uma percentagem ainda significativa de ligante metálico. Esta particulariedade leva a que não seja completamente linear a máxima de que a presença de tensões residuais de compressão controla e reduz a propagação de fendas por fadiga, uma vez que as falhas podem ocorrer pelo colapso de micro fissuras na superfície. Neste estudo o processo de eleição adoptado para a introdução de tensões na superfície da pastilha de corte, dentro da gama de tratamentos superficiais, foi o jateamento em meio húmido. Foram ensaiadas várias condições distintas de jateamento numa pastilha de corte com geometria simples. Estes corpos de prova foram avaliados por diversas técnicas de caracterização, sendo as mais relevantes a determinação da dureza por ensaios de identação e a determinação das tensões residuais por difração de Raios X. Os resultados do desempenho da pastilha de corte quando aplicada em torneamento e da adesão do revestimento da pastilha de corte previamente sujeita a jateamento são bastante animadores e comprovam os benefícios subjacentes à presença de tensões residuais de compressão numa ferramente de corte.
This study fits within the scope of innovation and continuous improvement of a very concrete business area, the cutting tools industry. The central focus is the development and perception of the relationship between the state of stress introduced in a cutting tool and the improvement or not of its mechanical and tribological properties therewith.The studied cutting pellets consist of tungsten carbide with cobalt, that is, it is a ceramic material with a still significant percentage of metal binder. This particularity leads to the fact that the presence of compressive residual stresses is not completely linear and reduces the propagation of cracks through fatigue, since the faults can occur due to the collapse of micro cracks in the surface.In this study the chosen process for the introduction of stresses on the surface of the cutting insert within the range of surface treatments was wet blasting. Several different blasting conditions were tested on a single geometry cutting insert.These specimens were evaluated by several characterization techniques, the most relevant being the determination of hardness by indentation tests and determination of residual stresses by X-ray diffraction.The results of the performance of the cutting insert when applied in turning and the adhesion of the sheeting of the cutting insert previously subjected to blasting are quite encouraging and prove the benefits underlying the presence of residual compression stresses in a cutting tool. In the future the purpose is the extrapolation of the results obtained to a more common and comercial available geometry.