A superfície (001) dos compostos III-V têm grande importância para as modernas tecnologias de crescimento de materiais, assim o estudo da formação dessa superfície, de suas propriedades e dos processos de adsorção de moléculas que ocorrem sobre ela é essencial para o desenvolvimento da ciência de materiais. Sabe-se que o InP, a exemplo de outros compostos III-V, apresenta uma variedade de padrões de reconstrução para superfície (001) que dependem das condições iniciais que prevalecem durante o seu crescimento. Neste trabalho estudamos os padrões da superfície InP(001) originados em ambientes com concentração máxima de átomos de índio e de fósforo e os processos envolvidos com a adsorção da molécula H2S sobre estas superfícies. Usamos cálculos de primeiros princípios dentro do formalismo da Teoria do Funcional da Densidade (DFT) associados à pseudopotenciais de norma conservada com aproximação generalizada do gradiente para o termo da energia de troca e correlação (DFT-GGA) e correlação não linear de caroço (NLCC). Fizemos a adsorção da molécula de H2S sobre os padrões mais estáveis da superfície InP(001), considerando os casos com a molécula dissociada e não dissociada. No padrão reconstrução 2x2 com dois dímeros, superfície originada em ambientes ricos em átomos de fósforo, fizemos o cálculo das barreiras de energia entre as configurações energeticamente mais favoráveis e encontramos um mecanismo de adsorção para a molécula de H2S dissociada Na superfície com padrão de reconstrução 2x4, crescida em ambientes ricos em átomos de índio, com formação de um dímero misto, verificamos que a molécula não dissociada adsorve sobre os sítios formados por átomos de fósforo e que adsorve sobre os sítios formados por átomos de índio. O átomo de enxofre da molécula dissociada adsorve sobre os sítios formados por átomos de fósforo e de índio e as moléculas de hidrogênio permanecem desorvidas, porém as estruturas são desfavoráveis energeticamente. / The (001) surface of the III-V compounds have great importance for modern technologies of materials growth thus the study of these surfaces formation, its properties and the absorption process of the molecules are essential for the development of materials science. It is well known that the InP, as well others III-V compounds, present a variety of reconstruction patterns for (001) surface that depend on the initial growth conditions. In this work we studied the patterns of InP(001) surface considering an environment with high concentration ln and P atoms and the interaction of the H2S molecule with these surfaces. Using first-principles calculations within the Density Functional Theory (DFT) formalism, norm-conserving pseudopotentials with the generalized gradient approximation for the exchange and correlation energies (GGA) and non-linear core-correction (NLCC). We have studied the H2S molecule adsorption on different reconstruction of the InP(001) surface, considering the cases in which the H2S molecule was dissociated and non-dissociated. In the 2x2 pattern with two dimmers, the energy barriers were calculated between the more energetically favorable configurations and a possible mechanism of adsorption of dissociated H2S molecule is proposed. The non-dissociated molecule does not bind over phosphorus sites but over indium sites, for all considered reconstructions. The sulfur atom of dissociated molecule adsorbs over phosphorus and indium sites and the hydrogen molecules stands not joint, however the structure are energetically unfavorable.

Das 3. Dresdner Werkstoffsymposium wurde am 6./7. Dezember im Westin Bellevue Hotel Dresden abgehalten. Das Thema lautete "Werkstoffoberflächen für Mensch und Technik".

Ceramic materials contain several defects, one of which is porosity. At the time of writing, porosity measurement is a manual and time-consuming process performed by a human operator. With advances in deep learning for computer vision, this thesis explores to what degree convolutional neural networks and semantic segmentation can reliably measure porosity from microscope images. Combining classical image processing techniques with deep learning, images were automatically labeled and then used for training semantic segmentation neural networks leveraging transfer learning. Deep learning-based methods were more robust and could more reliably identify porosity in a larger variety of images than solely relying on classical image processing techniques.

To compete with other manufacturing companies in the market, product design and manufacturing methods need to be improved constantly. To save time and money, there is an advantage if there is a manufacturing plan in place before designing the final product. Composites have been used worldwide for over 6,000 years and their use is expected to increase in the future. Composites offer advantages in product design and manufacturing since it can be adapted to the intended purpose.  The purpose of the project is to determine whether it is possible to produce a magnetic polymer composite with a sufficiently high magnetism to lift a specific weight. The purpose is fulfilled through practical executions together with a literature study to find out which materials were most suitable for the application. The polymer composites were tested in magnetic tests to see if a sufficiently high magnetism was obtained to lift the specific weight.  Two steel powders, differing in particle structure and density, were mixed with an epoxy as a binder and then cast in two different moulds with a depth of 2 mm and 4 mm. The proportions of the steel powder were tested from 50% up to 97%. The result showed that sufficiently high magnetism to lift the intended weight was reached at a concentration of steel powder between 85% - 97%. The composites did not exhibit the necessary magnetic capacity to function in the intended application and therefore further tests with a magnetic material with higher relative permeability are proposed. / Syftet med arbetet är att undersöka om det går att framställa en polymerkomposit med tillräcklig magnetisk kraft för att lyfta en skiva som väger 100g. Polymerkompositen ska tillverkas genom gjutning. De parametrar som behöver tas hänsyn till i arbetet är vilka material som är lämpliga att använda i kompositen, vilka proportioner av plast- och magnetiskt material som behövs för att skapa tillräcklig magnetisk kraft och den magnetiska kraft som polymerkompositen behöver erhålla för att lyfta skivan. Materialvalet är en viktig aspekt i arbetet för att uppnå önskat resultat. Det magnetiska materialet behöver ha en hög relativ permeabilitet, det vill säga en hög grad av förmågan att magnetisera sig själv med ett pålagt externt magnetfält, för att uppnå tillräcklig magnetisk kraft. Vid val av polymermaterial är det viktigt att ta hänsyn till materialets viskositet, med andra ord, materialets tjockhet. Det med anledning för att en lägre viskositet hos polymeren tillåter högre koncentration av metallpartiklar. Vilket är önskvärt för att få in så mycket magnetiskt material som möjligt i polymerkompsiten. Proportionerna av de två materialen behöver anpassas efter dess egenskaper för att uppnå en önskad magnetisk kraft. Ett magnetiskt material som har en hög relativ permeabilitet behöver till exempel blandas med ett polymermaterial med högre viskositet för att blandningen inte ska sedimentera.   Kompositer har använts i hela världen i över 6000 år och användningen förväntas att öka under framtiden. Grunden till detta projekt är att en stålbricka med magnetiska egenskaper ska bytas ut mot en magnetisk polymerkomposit i ett instrument. Fördelen med en komposit är möjligheten att anpassas efter ändamålet och därför till exempel kan vara lättare, tåligare, flexibla och motstå korrosion.  Genom praktiska undersökningar tillsammans med en litteraturstudie uppfylls syftet att ta reda på lämpliga material och proportioner. Avslutningsvis ska de gjutna polymerkompositerna testas i magnetiska tester för att undersöka om tillräckligt hög magnetism kan erhållas för att lyfta den specifika vikten. I arbetet används två stålpulver som skiljer sig i partikelstruktur och densitet, dessa stålpulver blandas med bindemedlet epoxi och gjuts därefter i två olika formar med djupet 2mm och 4mm. Proportionerna i vikt för stålpulvret testades från 50% upp till 97%. Resultatet visade att tillräckligt hög magnetism för att lyfta avsedd vikt nåddes vid en koncentration av stålpulver mellan 85% -97%. Resultatet visade inte tillräckligt hög magnetism för att fungera i den avsedda applikationen och därför föreslås vidare tester med ett magnetiskt material med högre relativ permeabilitet.

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High hardness steels can be affected by delayed brittle cracking often attributed to hydrogen embrittlement. Improved resistance to hydrogen embrittlement would be beneficial to many industries including military, automotive, and high-rise construction. While other prevention methods include coating, trapping, and barriers, design efforts in this study were focused on improving intrinsic properties to be more resistant to hydrogen embrittlement. Four alloys targeting 477 – 534 HB were designed and produced in-house and compared against a commercial grade 500 HB alloy. Charpy V-notch (CVN) impact toughness and tensile specimens were made according to ASTM E23 and ASTM E8 to characterize mechanical properties. Hydrogen embrittlement testing was performed using ASTM E8 test samples electro-chemically charged in either sodium hydroxide or sulfuric acid with thiourea in solution. Results suggested that alloying for lower strength and better toughness by reducing C and Mn results in lower hydrogen embrittlement susceptibility.

The new dihydrobis(4-cyano-3-tert-butylpyrazolylborate) ligand has been synthesized. Isolated crystals of the thallium complex were collected and structurally characterized by X-ray diffraction. Transition metal complexes of the ligand are currently under investigation.

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Ag is a widely used electrical contact material due to its excellent electrical properties. The problems with Ag are that it is soft and has poor tribological properties (high friction and wear in Ag/Ag sliding contacts). For smart grid applications, friction and wear became increasingly important issues to be improved, due to much higher sliding frequency in the harsh operation environment. The aim of this thesis is to explore several different concepts to improve the properties of Ag electrical contacts for smart grid applications. Bulk Ag-X (X=Al, Sn In) alloys were synthesized by melting of metals. An important result was that the presence of a hcp phase in the alloys significantly reduced friction coefficients and wear rates compared to Ag. This was explained by a sliding-induced reorientation of easy-shearing planes in the hexagonal structure. The Ag-In system showed the best combination of properties for potential use in future contact applications.  This thesis has also demonstrated the strength of a combinatorial approach as a high-throughput method to rapidly screen Ag-based alloy coatings. It was also used for a rapid identification of optimal deposition parameters for reactive sputtering of a complex AgFeO2 oxide with narrow synthesis window. A new and rapid process was developed to grow low frictional AgI coatings and a novel designed microstructure of nanoporous Ag filled with AgI (n-porous Ag/AgI) using a solution chemical method was also explored. The AgI coatings exhibited low friction coefficient and acceptable contact resistance. However, under very harsh conditions, their lifetime is too short. The initial tribotests showed high friction coefficient of the n-porous Ag/AgI coating, indicating an issue regarding its mechanical integrity. The use of graphene as a solid lubricant in sliding electrical contacts was investigated as well. The results show that graphene is an excellent solid lubricant in Ag-based contacts. Furthermore, the lubricating effect was found to be dependent on chemical composition of the counter surface. As an alternative lubricant, graphene oxide is cheaper and easier to produce. Preliminary tests with graphene oxide showed a similar frictional behavior as graphene suggesting a potential use of this material as lubricant in Ag contacts.