The function of titanium- and nickel-silicides is to lower the series resistance and contact resistivity in gate, source and drain contacts of an integrated circuit transistor. With decreasing dimensions, the low resistivity C54 TiSi2 is not formed and stays in its high resistivity phase C49. It was found that a layer of niobium interposed between titanium and silicon, which is supposed to promote the C54 phase, led to the formation of the high resistivity C40 (Ti,Nb)Si2 in both small and large contacts. Increased interest in Si1-xGex layers led to the inclusion of the Ni-Si-Ge system in this project. The interaction between nickel and poly-Si0.42Ge0.58 was found to be different from nickel and poly-silicon in the meaning of the phases formed during high temperature annealing. High-resistivity NiSi2 was formed at 750°C, but nickel and Si0.42Ge0.58 formed no disilicide. A massive out-diffusion of germanium from the NiSi1-uGeu resulted in agglomeration at lower temperatures than for NiSi. This was ascribed to the larger enthalpy of formation for nickel reacting with silicon than with germanium. Ternary phase diagrams, with and without the disilicide phase, were calculated. According to the tie lines, NiSi1-uGeu will be in thermodynamic equilibrium with Si1-xGex when u is smaller than x. This was confirmed experimentally, where a balanced germanium concentration in NiSi1-uGeu and Si1-xGex, stabilized the germanosilicide. When nickel interacted with strained and relaxed silicon-germanium it was established that a strained substrate led to a morphologically unstable NiSi1-uGeu. The germanosilicide was highly textured on both (001) and (111) substrates. The texturing was explained by the absence of Ni(SiGe)2 which forced NiSiGe to reorient so as not to resemble a digermanosilicide at the film/substrate interface. NiSi0.82Ge0.18 formed on p+-Si0.82Ge0.18 in CBKs grew laterally under the SiO2, defining the contact hole. The contact resistivity extracted by 3D modelling was 5×10-8 Ωcm2.

This thesis comprises tribological studies of extremely well-defined surfaces of different designs. Both low-friction and high-friction surfaces were manufactured and experimentally evaluated. In the low-friction studies, lithography and anisotropic etching of silicon was first used as a texturing technique. The textured surfaces were subsequently PVD coated with TiN or DLC to achieve tribologically relevant interfaces. The results showed that under starved lubricated conditions, fine surface textures lowered the coefficient of friction and the wear rate. It was shown that also the orientation of the texture is of major importance for the lubricating function. Further, a novel embossing technique was developed, permitting texturing of steel and other materials. A micro mechanically designed diamond tool was used to emboss steel surfaces. The roller/piston contact from a hydraulic motor was simulated and introduction of an embossed texture on the piston decreased the level and the fluctuation of the friction. The effect of the texture was here similar to the effect of an additional polish step. However, in general it is not an easy task to substantially improve a boundary lubricated contact by introducing a texture. Studies of high friction surfaces were performed on micro mechanically designed diamond surfaces equipped with sharp pyramids or ridges. Just as theory predicts, the coefficient of friction was dependent on the shape of the ploughing bodies, but not on the counter material or the load. The tested surfaces resulted in static coefficients of friction between 1.1 and 1.6, depending on surface design and orientation. These are extremely high values, and therefore very interesting for practical applications requiring a high static friction. Conclusively, the present thesis shows that it is possible to design and produce surfaces both for improved lubrication in sliding contact and for substantially improved high friction performance in static contacts.

Synthesis, nuclear structure, and magnetic properties of the perovskites: Nd0.7-xMgxSr0.3MnO3 (x=0.0, 0.1), Nd0.6Mg0.1Sr0.3Mn1-zMgzO3 (z=0.1, 0.2), LaCr1-yMnyO3 (y=0.0, 0.1, 0.2, 0.3) and La1-xNdxFe0.5Cr0.5O3 (x=0.1, 0.15, 0.2) have been studied. The structure of the samples was investigated by X-ray and Neutron powder diffraction and the magnetic properties were investigated by magnetization measurements using SQUID-magnetometry. All compounds have orthorhombic structure with spacegroup Pnma (No. 62). The compounds which had the composition Nd0.7Sr0.3Mn1-yMgyO3 by preparation, were found to attain the composition Nd0.7-xMgxSr0.3MnO3 and Nd0.6Mg0.1Sr0.3Mn1-zMgzO3. The x=0.0 and 0.1 compounds order in a pure ferromagnetic structure at about 200 K, but the Mn moments become slightly tilted and attain an antiferromagnetic component below 20 K. A ferromagnetic Nd moment also appears at low temperatures. The compounds with Mg substitution y=0.2 and 0.3 do not exhibit long range magnetic order, but local ferromagnetic correlations among the Mn moments appear below 200 K. At low temperature, also a local antiferromagnetic ordering of the Nd magnetic moments occurs. In these compounds, the Mn3+/Mn4+ ratio is reduced so that the double exchange interaction is suppressed and the antiferromagnetic superexchange interaction favoured. The samples of composition LaCr1-yMnyO3 have orthorhombic structure at room temperature and below. The magnetic properties of the system are markedly affected by Mn-substitution. The parent compound LaCrO3 is a pure G-type antiferromagnet with Néel temperature 290 K. With incresing Mn-substitution, a ferromagnetic component developes in the ordered phase bcause of canting of the magnetic moments. The degree of canting increases with increasing Mn-substitution and the magnitude of the antiferromagnetic component of the moment decreases. The system La1-xNdxFe0.5Cr0.5O3 has the same antiferromagnetic G-type structure as LaCrO3, but orders already at temperatures above 400 K and develops only a very weak ferromagnetic component of the magnetic moment at low temperatures.

Magnetic properties of diluted magnetic semiconductors and magnetic metallic multilayers are investigated by SQUID magnetometry. By doping GaAs with magnetic Mn2+ ions under well defined growth conditions, one obtains a diluted magnetic semiconductor, (Ga,Mn)As, in which the randomly-distributed magnetic ions act as acceptor centers. At high enough dopant and hole concentration a carrier-induced ferromagnetic state results between the magnetic ions. Due to peculiarities of the growth process sizable amounts of donor defects, such as Mn interstitials and As antisites, are also introduced into the GaAs host. The magnetic properties of (Ga,Mn)As are altered by the presence of such defects through the compensation effect of the holes. The Mn interstitials are thermally unstable above a certain threshold temperature and therefore their concentration can be controlled by post-growth annealing. The influence of the interfaces on the magnetic moment of FeNi/V and FeNi/Co superlattices has been studied. A decrease of the `FeNi' magnetic moment at the interfaces is observed for FeNi/V superlattices while in case of FeNi/Co an enhanced magnetic moment is obtained at the interfaces. Changes of the interlayer exchange coupling have been studied in a series of Fe/V(Fe) multilayers in which the V spacer was alloyed with small amounts of Fe. The dynamic magnetic properties of discontinuous metal-insulator multilayers of Ni81Fe19/Al2O3 have been investigated. By varying the thickness of the insulator the system exhibits a superferromagnetic, a 3d spin-glass-like and a superparamagnetic behavior.

Flax fibers, along with a number of other natural fibers, are being considered as an environmentally friendlier alternative of synthetic fibers in fiber-reinforced polymer composites. A common feature of natural fibers is a much higher variability of mechanical properties. This necessitates study of the flax fiber strength distribution and efficient experimental methods for its determination. Elementary flax fibers of different gauge lengths are tested by single fiber tension in order to obtain the stress-strain response and strength and failure strain distributions. The applicability of single fiber fragmentation test for flax fiber failure strain and strength characterization is considered. It is shown that fiber fragmentation test can be used to determine the fiber length effect on mean fiber strength and limit strain. The effect of mechanical damage in the form of kink bands and of diameter variability on the strength of elementary flax fibers is considered. Stiffness and strength under uniaxial tension of flax fiber composites with thermoset and thermoplastic polymer matrices are studied. The applicability of rule of mixtures and orientational averaging based models, developed for short fiber composites, to flax reinforced polymers are evaluated. Both the quasi-static and time dependent mechanical properties of flax fiber/thermoplastic starch based composites are analyzed. The effect of temperature and relative humidity is investigated. It is found that microdamage accumulation in this type of composites is not significant. Results show that the composite elastic modulus and failure stress are linearly related to the maximum stress reached by the matrix in tensile tests. Simple material models are suggested to account for the observed nonlinear viscoelasticity and viscoplasticity. / Godkänd; 2009; 20091029 (edgspa); DISPUTATION Ämnesområde: Polymera konstruktionsmaterial/Polymeric Composite Materials Opponent: Docent Kristofer Gamstedt, Kungliga Tekniska Högskolan, Stockholm Ordförande: Docent Roberts Joffe, Luleå tekniska universitet Tid: Onsdag den 9 december 2009, kl 10.00 Plats: E 231, Luleå tekniska universitet

<p>In this project, nano powder of CoSb₃ thermoelectric material was synthesized using chemical alloying novel co-precipitation method. This method involved co-precipitation of TE precursor compounds in controlled pH aqueous solutions followed by thermo-chemical treatments including calcination and reduction to produce nano-particulates of CoSb₃. The nano powder was consolidated using rapid solid state spark plasma sintering (SPS) and the processing time was of the order of few minutes. On a result very high densities were achieved and grain growth was almost negligible.</p><p>Various batches of the CoSb₃ nano powder were produced to achieve high purity, minimum particle size and compensate Sb evaporation during thermo-chemical reduction. For de-agglomeration, powder was grinded before and after calcination. Samples were characterized at each stage during synthesis using XRD and SEM (with EDX). Thermal gravimetric analysis (TGA) was done before thermochemical treatments to observe weight losses with heating the powder at high temperatures and other physiochemical changes. Thermal diffusivity of the samples was measured at room temperature using Laser Flash Apparatus (LFA) and heat capacity was measured using Differential Scanning Calorimetry (DSC).   Thermal conductivities are calculated using these thermal diffusivities, heat capacities and densities of the sintered pellets. Average grain size is measure using image size J software.</p><p>It was observed that powder purity and size is affected by batch size, reduction conditions like holding temperature and time.  During sintering with SPS; heating and cooling rates, sintering temperature, holding pressure and time were the main variables. Grain size and morphology was analyzed using SEM.</p><p>It was observed that larger the grain size higher will be the thermal diffusivity, which leads to increase in thermal conductivity. Hence, grain size has affected on thermal conductivity and also on TE performance.</p> / QC 20100708

<p>Hydrogen is abundant, uniformly distributed throughout the Earth's surface and its oxidation product (water) is environmentally benign. Owing to these features, it is considered as an ideal synthetic fuel for a new world energetic matrix (renewable, secure and environmentally friendly) that could allow a sustainable future development. However, for this prospect to become a reality, efficient ways to produce, transport and store hydrogen still need to be developed. In the present thesis, theoretical studies of a number of potential hydrogen storage materials have been performed using density functional theory. In NaAlH₄ doped with 3d transition metals (TM), the hypothesis of the formation of Ti-Al intermetallic alloy as the main catalytic mechanism for the hydrogen sorption reaction is supported. The gateway hypothesis for the catalysis mechanism in TM-doped MgH₂ is confirmed through the investigation of MgH₂ nano-clusters. Thermodynamics of Li-Mg-N-H systems are analyzed with good agreement between theory and experiments. Besides chemical hydrides, the metal-organic frameworks (MOFs) have also been investigated. Li-decorated MOF-5 is demonstrated to possess enhanced hydrogen gas uptake properties with a theoretically predicted storage capacity of 2 wt% at 300 K and low pressure.</p><p>The metal-hydrogen systems undergo many structural and electronic phase transitions induced by changes in pressure and/or temperature and/or H-concentration. It is important both from a fundamental and applied viewpoint to understand the underlying physics of these phenomena. Here, the pressure-induced structural phase transformations of NaBH₄ and ErH₃ were investigated. In the latter, an electronic transition is shown to accompany the structural modification. The electronic and optical properties of the low and high-pressure phases of crystalline MgH₂ were calculated. The temperature-induced order-disorder transition in Li₂NH is demonstrated to be triggered by Li sub-lattice melting. This result may contribute to a better understanding of the important solid-solid hydrogen storage reactions that involve this compound. </p>

<p>In this thesis a multilayer actuator structure is developed for the I-SWARM project. In order to build an energy efficient and low voltage actuator system for the 3x3x3 mm3 robot, the resonance drive mode in combination with a ten layer multilayer structure build upon the most suitable substrate material was used. Two different sizes of the locomotion module were built. The first one is five times larger than the small version. It has five active layers and is simpler to work with and to test. The small module has three 2x0.4 mm can-tilevers on a 3x3mm body and ten active layers.</p><p>The multilayer process involve easily defined flexible printed circuit (FPC) board as substrate material, spin coating piezoelectric poly(vinylidenefluoride- tetrafluoroethylene) P(VDF-TrFE) as active stack material, and evaporated aluminum electrodes on each active polymer layer. By using different shadow masks for each electrode layer, special inter con-tact areas can be contacted from above after the polymer has been removed by an Inductively Coupled Plasma (ICP) etch. The contours of the locomo-tion module was etched in a Reactive Ion Etch (RIE) equipment. Both the cupper layer in the FPC and the electrode layers of the active stack, were used as etch mask.</p><p>The deflections of the cantilevers were measured at low voltages to ensure as realistic drive voltage as possible for the I-SWARM robot. The large struc-ture showed a 250 µm deflection at 4 V and 170 Hz resulting in a Q-value of 19. The deflection of the small structure was 8 µm at 3.3 V and 5000 Hz and the measured Q-value was 31.</p>

<p>In the last few years people have become more and more aware of how humanity is affecting the climate. In the direction of reducing the greenhouse gases is to design engines with higher tensile properties and reduced weight, in order to achieve lower fuel consumption and cleaner fuel incineration in today's truck engines.</p><p>In order to achieve these requirements it’s necessary to increase the combustion pressure in the engine. This requires higher tensile properties and high thermal conductivity of the engine material. The department of Component Technology at the University of Jönköping in collaboration with Volvo Powertrain AB, Scania CV AB and DAROS Piston Rings AB has been commissioned to develop this material and to find knowledge of material properties used in truck engines and piston rings used for marine applications.</p><p>The purpose with this work is to analyze the tensile properties of a series of cast iron, cast under different metallurgical conditions.</p><p>Four different series of cast irons have been analyzed from four points of view, carbon concentration, nodularity, amount inoculation and cooling rate.</p><p>After the tensile test all specimen data was analyzed in a mathematic calculation program called Matlab 2006a. These results were plotted in different diagrams to show the relations between the variables.</p><p>A low carbon contents and high cooling rate result in high tensile properties and vice versa. Also, a high nodularity gives the same result, i.e. high ultimate tensile strength, yield strength and young’s modulus. The experiment which cover different amount of inoculation, shows that Superseed is the most efficient element to increased tensile properties followed by Fe-powder and Fe-C-powder.</p><p>Lamellar graphite iron has the highest thermal conductivity and vibration damping properties compared to compact graphite iron followed by nodular graphite iron. Researches show that the thermal conductivity increases with slow cooling rate, irrespective of graphite structure. When designing new diesel engines, high tensile properties as well as high thermal conductivity are wanted. Compact cast iron has a compromised quality of these requirements. Higher tensile properties are a higher priority than thermal conductivity when the casting cooling rate is chosen.</p> / <p>Mänskligheten har idag blivit allt mer medveten om vilken påverkan människan har på klimatet. Ett steg i att reducera växthusgaserna är att konstruera motorer med högre hållfasthet och reducerad vikt, detta för att uppnå lägre bränsleförbrukning och renare förbränning i dagens lastbilsmotorer.</p><p>För att uppnå dessa krav är en lösning att öka kompressionen i motorn. Detta medför högre hållfasthetskrav samt hög värmeledningsförmåga hos materialet i motorerna. Avdelningen för komponentteknologi på Tekniska högskolan i Jönköping har i samarbete med Volvo Powertrain AB, Scania CV AB och DAROS Piston Rings AB fått uppdraget att utveckla ett material med rätt mekaniska egenskaper för att passa i lastbilsmotorer och kolvringar i marina applikationer.</p><p>Målet med detta examensarbete är att analysera de mekaniska egenskaperna i en serie där gjutjärn gjutets under olika metallurgiska förhållanden.</p><p>Fyra olika serier av gjutjärn har analyserats med utgångspunkt av variation av kolhalt, nodularitet, mängd ympningsmedel samt svalningshastighet.</p><p>Efter dragning av samtliga prover analyserades mätdata i Matlab 2006a och resulterade i olika sambandsdiagram.</p><p>Låg kolhalt samt snabb avsvalning av gjutgodset ger höga hållfasthetsegenskaper och vice versa. En hög nodularitet ger höga hållfasthetsegenskaper gällande brottgrans, sträckgräns och elasticitetsmodulmodul. Från experimenten där olika ympningsmedels påverkan av hållfastheten, har kunnat konstateras att ympningsmedlet Superseed ger de högsta hållfasthetsegenskaperna följt av Fe-pulver och Fe-C-pulver.</p><p>Värmeledningsförmågan och dämpningsförmågan för vibrationer är bäst i lamellartad grafit följt av kompakt och nodulär grafit. Studier visar att värmeledningsförmågan ökar med långsam svalning, oavsett grafitstruktur. I dagens dieselmotorer eftersträvas både god hållfasthet och god värmeledningsförmåga. En kompromiss av dessa krav är gjutjärn med en kompakt grafitstruktur. Högre hållfasthet bör prioriteras före bättre värmeledningsförmåga när val av svalningshastighet för gjutgodset görs.</p>

Fusion welding is one of the most used methods for joining metals. This method has largely been developed by experiments, i.e. trial and error. The problem of distortion and residual stresses of a structure due to welding is important to control. This is especially important in the aerospace industry where the components are expensive and safety and quality are very important issues. The safety requirements and the high costs of performing experiments to find different manufacturing routes is the motivation to increase the use of simulations in design of components as well as its manufacturing. Thus, in the case of welding, one can evaluate the effect of different fixtures, welding parameters etc on the deformation of the component. The effects of previous processes are also important to consider, as well as it is important to bring forward the current state to subsequent processes.When creating a numerical model, the aim is to implement the physical behaviour of the process into the model. However, it may be necessary to compromise between accuracy of the model and the required computational time. The aim of the work presented in this thesis was to develop a method and model for simulation of welding and metal deposition of large and complex components using the finite element method. The model must be reliable and efficient to be usable in the designing and planning of the manufacturing of the component. In this thesis, the meaning of efficiency of a model is wider than just the computational efficiency. The time for creation and definition of the model should also be included. The developed methods enable the user to create a model for welding or metal deposition with a minimum of manual work. The method for defining weld paths and heat input together with activation of elements is now implemented in the commercial finite element software MSC.Marc. The implementation is based on the experience in this work and communication with the author. The approach has been validated against test cases. Naturally, this validation is dependent on sufficient accuracy of the heat input model and material model that are used. It is the first time a dislocation density model has been used to describe the flow stress in a welding simulation. The work has also demonstrated the possibility to calibrate heat input models with a physical based heat input model, thus relieving the need to calibrate the heat source versus measurements.Efficiency in terms of computing time has also been investigated in the course of this work. Three different methods has been explored and used, adaptive meshing, substructuring and parallel computation. The method that is found to be the most versatile and reduce the overall simulation time the most is parallel computation. It is straightforward for the user to employ and it introduces no reduction in the accuracy. / Godkänd; 2010; 20091124 (andlun); DISPUTATION Ämnesområde: Datorstödd maskinkonstruktion/Computer Aided Design Opponent: Professor Jesper Hattel, Danmarks tekniska universitet Ordförande: Professor Lennart Karlsson, Luleå tekniska universitet Tid: Fredag den 5 februari 2010, kl 09.00 Plats: E 243, Luleå tekniska universitet