The microsystem processing of today is based on an assortment of diverse and contrasting fabrication techniques, sprung from the microelectronic industry. Microsystem technology has primarily been developed to meet the demands for scaled down low-cost sensor and actuator systems. These devices are based on a number of contrasting principles, e.g. capacitance of mechanical membranes, microfluidic or piezoelectric actuation, electrostatic or heat deflection, etc. Clearly the disparate designs of these devices require microfabrication processes that are flexible and unrestricted, allowing deep and vertical structures to be obtained. The scope of this thesis is microstructuring and microsystem fabrication of primarily polymer materials by means of ion track lithography. Ion track lithography in combination with microstructuring unwraps unique and untouched grounds. The available building blocks in these microsystems include high aspect ratio (depth-to-width ratio) capillaries and metal wires of nanometric width, deep vertical cavities as well as conventional double-sided thin film lithographic patterns. The blocks have been combined to materialise a few technology demonstrators integrated in flexible polyimide foils and laminates, commercially attractive materials with excellent mechanical, temperature, and high frequency electronic properties. A magnetic field sensing structure based on the magnetoresistance as well as inductor coils for microwave circuitry have been fabricated and characterised. The various fabrication processes have been evaluated with respect to resolution, aspect ratio, and verticality. We can present a deep vertical micro? and nanofabrication technique, overriding the natural anisotropy or isotropy of many of the diverse materials employed in the microsystem field. We have obtained pores, capillaries with aspect ratios of up to 400, clusters of electrodeposited magnetic and non-magnetic nanowires with similar aspect ratio, solid complex structures with close to vertical walls as well as through hole microvias in flexible printed circuitboards.

In the modern process of continuous Direct Chill (DC) hot top casting of aluminium extrusion ingot with gas slip, poor surface quality of the cast ingot can still be a problem. In the worst cases pronounced surface wrinkling may occur coupled with periodic zones of reduced grain size, macrosegregation and exudation at the surface. The observed surface irregularities are believed to be linked to periodic oscillations or folding of the free molten aluminium surface in the mould, the meniscus, resulting in varying solidification conditions. The focus of this work is to gain a better understanding of the dynamics of the meniscus and the effect it has on ingot surface formation.

Thermal spraying is the name of a large group of coating deposition techniques used to deposit thick layers for a variety of applications. The principle is to melt the material, and rapidly propel the droplets towards a substrate where they flatten and solidify. When properly used, the substrate is not significantly heated. Spraying enables deposition of practically any material with a stable molten phase, on any solid material. Sprayed ceramics are used to reduce wear by sliding and by hard particles. However, due to the defect-filled microstructure resulting from spraying, the coatings typically have poor mechanical and tribological properties compared to dense, sintered materials. By varying the spraying parameters, the microstructure of the coatings was influenced, and also the wear rate and cohesion, which is difficult to quantify. Improved tribological properties resulted from spraying with axial particle injection equipment and using narrowly size distributed, spherically shaped powder particles, compared to conventional equipment and powder particles. A new method to seal the open pores of sprayed ceramic coatings by electrolysis is proposed and evaluated. It was found that almost complete sealing could be obtained, in some cases giving a drastically improved wear behaviour. The studied electrolytically deposited sealants were Pb, Sn, Cu and Ni. The latter was found to give the best performance. It also proved possible to apply PVD coatings to the sprayed ceramics, and it was shown that sprayed and Ni-sealed alumina can be superior to ball bearing steel to support thin, low friction PVD coatings.

The lateral double-diffused MOS (LDMOS) transistor has traditionally been a high-voltage device used in switching applications. The use as a high-frequency device has become more important lately since the LDMOS offers an low cost solution for telecommunication applications. An important property of the LDMOS concept is that it can be manufactured in virtually the same process used in standard CMOS production. It only requires one extra process step, which is easily implemented. The other important aspect that gives the LDMOS the good high-frequency performance is that the channel length is a process parameter and not a lithography parameter. This thesis investigates the LDMOS transistor primarily from two aspects. The first is the high-voltage performance. For a high-voltage device the most important parameter is the breakdown voltage. The second most important parameter is the on-resistance that has the property of being in contradiction of the breakdown voltage and usually trade-offs are made to achieve acceptable performance. In the thesis several methods to improve the breakdown voltage/on-resistance relation are presented. The other part covers the high-frequency behavior of the LDMOS transistor. High-frequency characterization has been made to gain valuable information for the fundamental understanding of the physical mechanisms inside the transistor. A large part of the thesis covers modeling and parameter extraction of the devices. A new general method for parameter extraction of small-signal equivalent circuit models is presented, which has the appealing properties of not needing any approximation during the extraction which is common with other techniques.

QC 20101020

In the turbine industry today, thermal barrier coatings are a commonly used, these are 0.1-2mm thick. So to be able to do some type of mechanical testing to receive material data so one can build an opinion regarding the health of the material. One needs a procedure that can work with small specimens and achieve clear results that can be transformed and compared with known data and known procedures. One of those methods is Small Punch Testing. This thesis describes one way to develop and test a functioning prototype of a Small Punch Testing device. The thesis includes; the reason it was developed in the beginning and how it has been developed throughout the decades, also in which areas the main research is made. It also shortly describes a working procedure in Ansys to get a Finite Element Method [FEM] model working. This method showed itself as useful, when just a small sample is at hand. The trials in this thesis also show that repetitive test can be done with good results which can be compared with real and FEM analysis data such as σ uts· / Inom turbin industrin idag så är keramiska värme barriärer vanligt förekommande dessa är normalt 0,1-2mm tjocka. För att kunna utföra mekanisk provning som grund för att bilda en åsikt om materialets kondition. Så behöver man en metod som kan åstadkomma tydliga data med små provbitar, Small Punch Testing är en av dem. Den här rapporten beskriver hur man kan gå tillväga för att få en fungerande prototyp. Den tar upp metodens ursprung och hur den har utvecklats under år tiondena, också mot vad den nuvarande forskningen riktar sig. Den beskriver även kort hur man ställer upp en finita element metod [FEM] modell i Ansys. Metoden visade sig användbar när man bara har en liten provbit att tillgå. Försöken visade att repetitiva tester kan göras med bra resultat som går att jämföra med verkliga och FEM analys data.

<p>The main objective of this industrially important work was to gain an increasing understanding of the properties of materials such as CMSX-4 nickel base super alloy, mould powder used in continuous casting of steel and coke used in blast furnace, with special reference to the thermal diffusivities. The measurements were carried out in a wide temperature range, solid, liquid, glassy and crystalline states.</p><p>For CMSX-4 alloy, the thermal conductivities were calculated from the experimental thermal diffusivities. Both the diffusivities and conductivities were found to increase with increasing temperature. Microscopic analysis showed the presence of intermetallic phases such as NiTi and NiTi2 below 1253 K. In this region, the mean free path of the phonons is likely to be limited by scattering against lattice defects. Between 1253 K and solidus temperature, these phases dissolved in the alloy adding to the impurities in the matrix, which, in turn, caused a decrease in the thermal diffusivity. This effect was confirmed by annealing the samples at 1573 K. The thermal diffusivities of the annealed samples measured at 1277, 1403 and 1531 K were found to be lower than the thermal diffusivities of non-annealed samples and the values did not show any noticeable change with time. It could be related to the attainment of equilibrium with the completion of the dissolution of γ and γ´ phases during the annealing process.</p><p>Liquid CMSX-4 does not show any change of thermal diffusivity with temperature. It may be attributed to the decreasing the mean free path being shorter than characteristic distance between two neighbouring atoms.</p><p>On the other hand thermal diffusivities of mould powder having glassy and crystalline states decrease with increasing temperature at lower temperature and are constant at higher temperature except for one glassy sample.</p><p>Analogously, the thermal diffusivity measurements of mould powder did not show any significant change with temperature in liquid state. It is likely to be due to the silicate network being largely broken down.</p><p>The thermal diffusivity is increased with increasing crystallisation degree of mould powder, which is expected from theoretical considerations.</p><p>The coke sample, taken from deeper level of the blast furnace, is found to have larger thermal diffusivity. This could be correlated to the average crystallite size along the structural <i>c</i>-axis, L_c, which is indicative of the higher degree of graphitisation. This was also confirmed by XRD measurements of the different coke samples. The degree of graphitisation was found to increase with increasing temperature. Further, XRD measurements of coke samples taken from different levels in the shaft of the blast furnace show that the graphitisation of coke was instantaneous between room temperature and 1473 K.</p>

No description available.

<p>Regarding the use of material, modern lightweight car bodies are becoming more and more complex than previous constructions. The materials nowadays are used for a more specific field of application and more high strength steels are used and also other materials like aluminium, stainless steel, reinforced polymers are used more frequent. The joining of these materials often requires new or modified joining processes. The aim with this thesis is concerned with the development of simulation models of the joining process as well as mechanical properties of self piercing riveted (SPR) joints and pierce nut joints. In both of these joining methods problems occur when introducing more high strength steel sheets. For SPR, fractures occur in the rivet, and for pierce nut the thread will be damaged.</p><p>Since both the SPR process and the pierce nut process expose the material for plastic deformation up to 150%, correct material properties for very large strain and a simulation program that could handle this was required. With the commercial finite element program Deform2D an axi-symmetric model has been built for the SPR process and the pierce nut process. Because of the computational time, 3D simulations were only used where it was necessary. The developed 3D models use the commercial finite element program ABAQUS-Explicit. All simulation models have been verified with satisfactory agreement to experimental results.</p><p>For SPR, an axi-symmetric simulation model was used for evaluating and optimising the setting process in the stainless steel sheets EN1.4301, HyTens 800 and HyTens 1200. Subsequently, 3D models were used for predicting the mechanical properties of new SPR joints that have showed reduced risk for rivet cracking. In pierce nut simulations, nuts with hardness 8 and 10 have been set in the high strength steel sheet DP600. An axi-symmetric simulation model was used for centred nut setting and two different simulation models in 3D were used to evaluate eccentric nut setting and torque resistance.</p><p>This work resulted in more knowledge about the fracture risk in the rivet and how to reduce it. The strain and stress, which was used as fracture indicators, were reduced to the half with modifications of the rivet and the die geometry. Mechanical property simulations in shear and peel load resulted in satisfactory results for new SPR joints that have showed reduced fracture risk during rivet setting. New die and rivet designs can be developed effectively by combining the process and mechanical property simulations.</p><p>For a pierce nut joint in high strength steel sheets (1.5mm DP600), the simulations show that the cutting of the sheet in combination with eccentric setting over the die causes the thread damage. The thread damage can be avoided by changing the dimension of the nut or by increasing the strength of the nut material. The simulation models can also be used to develop new nut and die geometries for future applications.</p>

<p>The aim of the present work was to clarify the mechanisms of hydrogen removal during vacuum degassing. The main reason for this was because the primary source of hydrogen pick-up in steel-making is the moisture in the furnace atmosphere and the raw material charged into the ladle furnace. Previous studies showed that the presence of hydroxyl ions in the ladle slag results in hydrogen transfer from the slag back into the steel bath. The main focus of this thesis was therefore to gain deeper knowledge of the ladle slag and its properties. For this purpose a number of slag compositions were examined in order to clarify whether these slags were single liquids at 1858 K. 14 out of 27 compositions in the Al₂O₃ CaO MgO SiO₂system was completely melted. These results were in disagreement with the existing phase diagrams.</p><p>Water solubility measurements were carried out by employing a thermo gravimetric technique. The temperature was found to have negligible effect on the water solubilities. The experimental results showed that the water capacity values varied between 1x10³and 2x10³ in the majority of the composition range. However, for compositions close to CaO saturation the water capacity value could reach higher than 3x10³. The experimental determined water capacity was further used to develop a water capacity model for the quaternary slag system Al₂O₃CaO MgO SiO₂. The model was constructed by considering the affects of the binary interactions between the cations in the slag on the capacity of capturing hydroxyl ions. The model calculations agreed well with the experimental results as well as with the literature data.</p><p>An attempt was made to develop a preliminary process model for dehydrogenation by using the results from CFD calculation. For this purpose industrial sampling was made during vacuum treatment. The hydrogen concentrations decreases fast in the initial stages of the degassing, but is slowed down in the final stage. The model calculations fit the initial stage of the dehydrogenation process well. In the final stage of the process the predicted values are somewhat lower than the plant data. The results from the model prediction showed that a dynamic process model could be satisfactorily constructed using the results from CFD calculation.</p><p>The present work aimed at determining how big impact hydroxyl ions in the slag have on the final hydrogen concentration in the liquid steel. It was found that the effect is of less importance regarding the final concentration of the metal after the degassing treatment.</p>