Thesis (MTech. : Engineering Metallurgy.)--Tshwane University of Technology, 2010. / Establish a qualitative and quantitative comparison between the parameters of the laser used in manufacturing a 120 mm curvature in HSLA steel parts and the micro-structural changes in the steel part. Subsequently, the final microstructure will be used to determine the reason for the poor fatigue performance of the HSLA steel after laser forming.

Orientadores: Lisandro Pavie Cardoso, Marco Sacilotti / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-08T18:38:56Z (GMT). No. of bitstreams: 1 Chiaramonte_Thalita_D.pdf: 12073771 bytes, checksum: d01b6c585fd5556757aea0542ecf63f2 (MD5) Previous issue date: 2007 / Resumo: Os nitretos (Ga, Al, In)N assim como os compostos GaInP, GaCuO2, representam um sistema de materiais muito importante para as aplicações em opto-eletrônica e dispositivos tais como os diodos emissores de luz (LEDs), lasers e nanosensores. Entretanto, o requisito essencial para as aplicações industriais desses materiais é a redução em seus tamanhos. Neste trabalho foram crescidos materiais metálicos formados por nitretos de gálio e também de semicondutores do tipo GaInP, GaCuO2 na forma de estruturas 3D, pela técnica de deposição química de organometálicos em fase vapor (MOCVD). Foi utilizado como precursor organometálico (OM) o trimetil gálio Ga(CH3)3e o nitrogênio N2 como gás portador. A temperatura e a pressão foram controladas durante o crescimento variando entre 500 e 750 o C e 100 a 760 Torr, respectivamente. Duas classes de estruturas 3D foram obtidas a partir da decomposição total ou parcial do gás pre-cursor, devido a interação entre o OM e o substrato que gera diferentes morfologias: i) as ligas metálicas (Ga, Al, In) formando estruturas semelhantes a balões, cetros (hastes com terminações esféricas) e neurônios, todos apresentando uma fina membrana de carbono amorfo que reveste a estrutura. Após o crescimento, estas estruturas foram submetidas ao processo de nitretação sob atmosfera de NH3 para transformá-las em micro/nanocristais de GaN; ii) os fios semicondutores micro/nanométricos com uma esfera metálica em sua terminação (bambus e cetros) . Na formação de ambas as estruturas, os precursores OM são como moléculas catalisadoras do crescimento. Este crescimento é considerado como um método alternativo e original para se obter estruturas 3D. Uma possível associação com o modelo apresentado pelo mecanismo de crescimento Vapor-Líquido-Sólido (VLS), que utiliza uma partícula metálica para promover os nanotubos de carbono e os nanofios semicondutores, ainda está em discussão. Informações estruturais e ópticas dessas novas estruturas crescidas sobre substratos de Cu (grade de difração), Si (001), InP (policristalino) e Al/SiO2/Si (fotolitografia) foram obtidas através da caracterização por difração de raios-X, microscopia eletrônica de varredura e de transmissão em alta resolução, espectroscopia por energia disper-siva, catodoluminescência e a espectroscopia de excitação por dois fótons. Nas amostras nitretadas, micro/nano cristais de GaN obtidos da liga de Ga aparecem impregnados no carbono turbostrático (folhas de carbono sem orientação obtidas do amorfo) que revestem as estruturas, e emitem na região do espectro l £ 365 nm, devido às suas dimensões quânticas. As hastes das estruturas do tipo bambus apresentam nódulos formados por discos monocristalinos de GaInP rotacionados de 60 o um em relação ao outro. Óxidos CuGaO2 e CuGa2O4compondo nanofios, denominados cetros, também foram obtidos / Abstract: Nitride (Ga, Al, In)N as well as GaInP, GaCu O2 compounds represent a very important class of materials to be used in the opto-electronic and devices applications such as light emission diodes (LEDs) lasers and nanosensors. However, the essential requirement to the industrial applications of these materials is the reduction in theirs sizes. In this work 3D structures based on gallium nitride and also GaInP, GaCuO2 semiconductors were grown by metalorganic chemical vapor deposition (MOCVD) technique. Trimethyl-gallium Ga(CH3) was used as the metal-organic (MO) precursor and nitrogen N2as carrier gas. During the growth to the temperature and pressure intervals of 500 - 700 oC and 100 - 760 Torr, respectively. Two 3D material classes were obtained from the total or partial precursor gas decomposition, since the interaction between the MO compound and the substrate gives rise to different morphologies: i) (Ga,In,Al) metallic alloys form ballons, scepters (wires with spherical ends) and neurons like structures, all involved by a thin carbon amorphous membrane. After growth, these structures were turned into GaN micro/nanocrystals by nitridation process under NH3 atmosphere; ii) micro/nanometer semiconductor wires with a metallic sphere at its end (bamboos and scepters). In order to form both structures, the MO precursors are taken as a catalyst molecule of the growth process. This is an alternative and original method to obtain 3D structures and a possible association to the model used in the vapour-liquid-solid (VLS) growth mechanism, in which a metallic particle promotes the carbon nanotubes and semiconductors nanowires is still under discussion. Structural and optical informations on these new structures grown on Cu (diffraction grid), Si(001), InP (polycrystalline) and Si/Al (photolithography) substrates were obtained through the characterization by X-ray diffraction, scanning electron microscope, high resolution transmission electron microscopy, en-ergy dispersive x-rays, cathodoluminescence and two photon excitation. In the nitrided samples, GaN micro/nanocrystals obtained from Ga alloy appear embedded in the turbostratic carbon (C sheets at random obtained from the amorphous) which involves the structures and, they emit in the l £ 365 nm region specter, due to their quantum dimensions. The bamboo rods present nodes consisting of GaInP single crystal discs turned by 60o one with respect to the other. The CuGaO2 and CuGa2O4 oxides compounding nanowires, called scepters, also were obtained. / Doutorado / Física / Doutor em Ciências

Themen wie Verfügbarkeit der Rohstoffe, Materialsubstitution, Umweltverträglichkeit, Schonung der Ressourcen, aber auch Produktionskosten werden immer häufiger als Bewertungskriterien herangezogen. Die Notwendigkeit der intensiven Zusammenarbeit unterschiedlicher Fachdisziplinen rückt immer mehr in den Mittelpunkt, wenn innovative Lösungen für neue Anwendungen gefragt sind. Das Projekt AMARETO wurde mit dem Ziel initiiert, im Rahmen einer engen Kooperation der TU Bergakademie Freiberg, der TU Dresden, der TU Chemnitz und des Fraunhofer IWU deren herausragende Spitzenforschung zusammenzuführen und praxisnah umzusetzen, um die anwendungsnahe Forschung weiter voranzutreiben und den wissenschaftlichen Vorlauf in Sachsen wertschöpfend zu verankern. Unter dem Motto »Vom Werkstoff zum ressourcenschonenden Produkt« trafen sich am 31. Mai 2018 Vertreter von Politik, Wirtschaft und Wissenschaft in Chemnitz zum ersten AMARETO-Kolloquium, um aktuelle Fragestellungen in den Bereichen Werkstoff-, Bauteil und Prozessentwicklung zu diskutieren. Im vorliegenden Tagungsband berichten die Projektmitarbeiter und -leiter gemeinsam über ihre aktuellen Forschungsergebnisse. Wesentlicher Ansatz des Projekts AMARETO ist es, die im Rahmen der Produktentstehung zu bearbeitenden Teilaufgaben – Entwicklung der Werkstoffe, Gestaltung und Dimensionierung von Bauteilen sowie Erarbeitung von Produktionsstrategien – enger miteinander zu verknüpfen und parallel sowie abgestimmt zu bearbeiten. Dies spiegelt sich im Tagungsband durch die Einbeziehung der Bereiche Smart Material, Smart Design und Smart Production wider. / Topics such as availability of raw materials, material substitution, environmental compatibility, conservation of resources, but also production cost are increasingly used as criteria for evaluation. The need for intensive cooperation between different disciplines becomes more and more important when innovative solutions for new applications are required. The AMARETO project was initiated with the aim of bringing together the outstanding top-level research of TU Bergakademie Freiberg, TU Dresden, TU Chemnitz and Fraunhofer IWU within the framework of close cooperation. A further project goal is the implementation of this research in a practical manner in order to further advance application-oriented research and anchor the scientific lead in Saxony in a value-adding manner. On 31 May, 2018 representatives from politics, industry and science met in Chemnitz for the first AMARETO colloquium under the heading 'From material to resource-saving product' to discuss current issues in the areas of development regarding materials, components and processes. In these conference proceedings, the project members and managers report together on their current research results. The main approach of the AMARETO project is to closely link the required subtasks of product development with each other - development of materials, design and dimensioning of components as well as the development of production strategies - and to work on them in parallel and in a coordinated manner. This is reflected in the conference proceedings due to the inclusion of the areas of Smart Material, Smart Design and Smart Production.