<p>This thesis treats angle-resolved optical properties and the energy efficiency of windows. A theoretical evaluation of optical and thermal properties of windows is briefly surveyed and the energy performance of a large selection of windows, under different conditions, is examined. In particular, angle dependent optical properties are analysed. A new model assessing angle dependence of the total solar energy transmittance, g, of windows is presented. A comparison of simple models for angle-dependence prediction has been performed, including both fictitious and measured real window glazings. The new proposed model illustrates low errors for both the real and the fictitious glazings. The impact of inaccuracy in the angle dependence of the g-factor has been assessed and found to be clearly noticeable but not necessarily critical. </p><p>A simple model for comparing the energy efficiency of different windows in different types of buildings and different climates has been further developed and analysed for several conditions. The energy performance of a large number of windows has been analysed using this model, and also by using other building and window simulation models. Typical savings when changing from a standard double glazed window to the optimal window for the investigated case is in the order of 100-150 kWh/m²yr. The annual energy balance of modern low emittance windows illustrates that they can be annual energy savers rather than energy losers, unlike traditional windows. However, it is shown that it is not important to argue about small changes (~0.01) of the thermal emittance value. Furthermore, advance solar control glazings effectively reduce solar transmittance with maintained high light transmittance. </p><p>AR-coatings and low-iron glazings can increase the transmittance of glazings considerably. In fact, a "super" low emittance window with a U-value below 1 W/m²K can have higher light transmittance than a common double-glazed unit. Windows with variable transmittance, switchable windows, are compared with high-performing solar control windows, illustrating some degree of potential energy savings compared to high performing static solar control windows, depending on the type of control that is used. This is accompanied by the potential for automatic thermal comfort- and glare control. </p><p>Different models for energy rating of windows have been evaluated, demonstrating that a simple linear rating depending on the U and g-factor of the window may be sufficient with certain restrictions. Division into climate zones is essential. </p><p>In all, the results demonstrate that energy-efficient windows provide huge energy-saving potentials on a large (regional, national, global) scale. </p>

<p>Magnetic properties of nanoparticle systems and spin glasses have been investigated theoretically, and experimentally by squid magnetometry.</p><p>Two model three-dimensional spin glasses have been studied: a long-range Ag(11 at% Mn) Heisenberg spin glass and a short-range Fe_0.5Mn_0.5TiO₃ Ising spin glass. Experimental protocols revealing ageing, memory and rejuvenation phenomena are used. Quantitative analyses of the glassy dynamics within the droplet model give evidences of significantly different exponents describing the nonequilibrium dynamics of the two samples. In particular, non-accumulative ageing related to temperature-chaos is much stronger in Ag(11 at% Mn) than in Fe_0.5Mn_0.5TiO₃.</p><p>The physical properties of magnetic nanoparticles have been investigated with focus on the influence of dipolar interparticle interaction. For weakly coupled nanoparticles, thermodynamic perturbation theory is employed to derive analytical expressions for the linear equilibrium susceptibility, the zero-field specific heat and averages of the local dipolar fields. By introducing the averages of the dipolar fields in an expression for the relaxation rate of a single particle, a non trivial dependence of the superparamagnetic blocking on the damping coefficient is evidenced. This damping dependence is interpreted in terms of the nonaxially symmetric potential created by the transverse component of the dipolar field.</p><p>Strongly interacting nanoparticle systems are investigated experimentally in terms of spin-glass behaviour. Disorder and frustration arise in samples consisting of frozen ferrofluids from the randomness in particle position and anisotropy axes orientation. A strongly interacting system is shown to exhibit critical dynamics characteristic of a spin-glass phase transition. Ageing, memory and rejuvenation phenomena similar to those of conventional spin glasses are observed, albeit with weak temperature-chaos effects.</p>

<p>Magnetic and electrical properties of selected compounds containing manganese (Mn) are investigated by SQUID magnetometry and transport measurements.</p><p>(Ga,Mn)As is a magnetic semiconductor obtained from GaAs by substituting Ga³⁺ for Mn²⁺. Mn acts in the alloy as a magnetic impurity, as well as a hole dopant. A carrier mediated ferromagnetic interaction is observed in (Ga,Mn)As single layers, as well as in (Ga,Mn)As/GaAs superlattices. The magnetic and electrical properties of these structures are controlled by the amount of holes, and thus by the amount of compensating defects such as As_Ga antisites. Magnetic inhomogeneity appears for thin layers as well as for layers containing large concentration of Manganese.</p><p>In non magnetic metallic elements containing a small amount of manganese impurities, a magnetic interaction develops, oscillating in sign with the distance between Mn atoms. Due to random distribution of manganese in a Ag(Mn) alloy, competing ferromagnetic and antiferromagnetic interaction appears, yielding magnetic frustration and the appearance of a spin glass phase at low temperature. These disordered systems show aging, chaos and memory phenomena, which are investigated in the three dimensional Ag(Mn) and Fe_0.5Mn_0.5TiO₃ spin glasses using time dependent magnetization measurements.</p><p>Perovskite manganites of type (R³⁺_1-xA²⁺_x)MnO₃ show colossal magnetoresistive e_ects (CMR). For an optimum doping x, a ferromagnetic order is established, and large changes of their electrical resistance with an applied magnetic field are observed; a magnetoresistance which can be tailored by adding oriented grain boundaries in thin films of these materials. The Manganese appears in the system as Mn³⁺ and Mn⁴⁺, and both ferromagnetic and antiferromagnetic interaction is mediated by the charge carriers along the Mn-O-Mn bonds of the perovskite structure. Depending on the cations forming the manganite, and their relative amount, glassy dynamics may appear, yielding aging and memory features similar to those observed in spin glasses.</p>

<p>This thesis treats charged particle transport, mostly in solid materials but also, to some extent, in aqueous media. Three major types of materials have been investigated; dielectric materials, ion conductors, and drug-delivery systems.</p><p>The frequency-dependent dielectric permittivity of sputtered amorphous thin film tantalum oxide (Ta₂O₅) has been determined by using impedance spectroscopy. A new interpolation formula has been derived, that interpolates between the two power-law regions at low and high frequencies usually observed in the dielectric spectrum. This formula is based on a regular-singular-point (RSP) analysis of the conduction process, and the power-laws in the dielectric spectrum are interpreted in terms of RSPs of the underlying rate equation for the corresponding polarization-current response function.</p><p>Lithium transport properties of Ta₂O₅ have been analyzed by using the galvanostatic intermittent titration technique and by isothermal transient ionic current measurements. Chemical and component diffusion coefficients for intercalated lithium have been extracted. Moreover, the ion conduction process has been analyzed theoretically, and expressions for transient ionic currents derived, both for single ion-conducting layers and for three-layered structures of ion conductors.</p><p>Electrical measurement techniques have also been applied to pharmaceutical systems. The alternating ionic current technique has been developed as a tool for determining the release of electrically charged drug substances in aqueous media. Tablets made of agglomerated micronized cellulose have been investigated, and sodium chloride has been used as a model drug. An attempt has been made to describe the combined drug dissolution and drug release processes in mathematical terms.</p>

<p>Clearly, there is a need for simple, strong actuators capable of large strokes in miniaturized systems such as valves and optical shutters.</p><p>The basis for this work is the microstructure technology with processing techniques adopted from the integrated circuit industry. In many cases alternative techniques have been developed to obtain features not achievable with conventional silicon technology. Techniques to fabricate thermally activated phase transition actuators capable of large strokes, as well as strong, piezoceramic actuators, have been investigated</p><p>Multilayered piezoceramic actuators have been fabricated and used in a miniature linear motor. A technique to build freestanding, three-dimensional structures drop by drop using a micromachined ink jet head and a slurry of piezoceramic particles has been developed. Ion track technology was used to create narrow pores in polyimide. To make bimorph-like structures capable of large strokes, these pores were impregnated with paraffin- a material with a large volume expansion associated with its solid-to-liquid phase transition. Paraffin was used in a silicon thermal switch intended for a passive thermal control system, and in a device to be used as a valve in a gas regulation system. Finally, paraffin actuators for integration in thermoplastic microfluidic systems have been developed. </p><p>During the course of this work not only the importance of identifying the best materials for a given application has been addressed and acknowledged, but also that of finding a processing route on occasion far from the conventional one, and perhaps most important, that of anticipating the often surprising effects following from miniaturization.</p>

<p>Challenges in the realisation of a miniature robot are both to handle the complexity of such a system, and to cope with effects of the actual reduction in physical size of all the parts. In particular, the mechanisms for locomotion have to be analysed.</p><p>The main achievements presented in the thesis are the evaluation and the development of fabrication techniques for miniature multilayer piezoceramic actuators, the evaluation of different motion mechanisms for miniature robots, and the development of building techniques for piezo-based miniature robots.</p><p>New piezoelectric drive units for miniature robots were designed and fabricated. To realize these monolithic devices, the fabrication technique for multilayer piezoceramic structures was further developed and evaluated with respect to the potential for miniaturisation. Introducing milling in the green state as a technique for shaping piezoceramic actuators gave a geometrical freedom without impairing the possibility of miniaturisation. A rapid prototype process was also developed. In this process, green machining in a milling machine was not only used to shape the multilayer structure, but also to pattern the internal electrodes. The first prototype was a multilayer telescopic actuator, which proved to have a displacement amplification of about 5 compared to a multilayer stack.</p><p>The drive units were used to evaluate different motion mechanisms. Experiments showed that for a mass corresponding to a typical miniature robot, i.e. 1-10 g, it is possible to use both dynamic and quasistatic motion mechanisms. Artefacts due to vibrations were identified as the main reason for non-ideal behaviour when the movable mass is small. Design criteria for robots with small masses are presented.</p><p>A tethered cm3 miniature robot for micromanipulation was successfully built. Application specific integrated circuits and two drive units were integrated with a particular building technique. Three-axial positioning and manipulating operations were demonstrated, allowing for a 5-axial movement of a tool.</p>

<p>This thesis presents the results from the development process of a ceramic dental filling material based on calcium aluminate cement. The main focus of the work concerns dimensional changes during setting, hardening and curing and the understanding of the factors controlling the dimensional stability of the system. A range of compositions for research purposes and the composition of Doxadent™ – a dental product launched on the Swedish market in October 2000 – were evaluated. Furthermore hardness characteristics, flexural strength, porosity and microstructure studies are presented. The studies of dimensional changes led to a thorough investigation of the measuring devices used and their relevance. A split pin expander technique, very simple in function, has been evaluated and improved. The technique is considered to be adequate for detecting dimensional stability in restrained samples, thus mimicking the case for real fillings in most tooth cavities. The dimensional changes in the calcium-aluminate based cement system are mainly controlled by the grain size, the exact composition and the compaction degree. The expansion of the calcium-aluminate cement system was in the early work decreased from several percent down to only tenths of a percent. Results show that Doxadent™ has less than 0.2% in linear expansion after 200 days of storage in water. However, long-term tests have been unable to verify whether expansion stops with time. Long-term in-vitro studies of dimensional changes also affect the test equipment used, which is why the long-term behavior of the dimensional stability has to be clinically evaluated. The material integrates excellently with the tooth structure, has hardness and thermal properties similar to those of enamel and dentine, and is also biocompatible during hardening. A patented process for the preparation of wet compacted specimens was also developed.</p>

<p>This thesis mainly treats the fabrication and applications of micro-optical elements in the semiconductor materials gallium arsenide (GaAs) and diamond.</p><p>The recent trend in high-capacity data transfer using light as the information carrier creates new demands on the optoelectronic systems, such as small size, low cost and the integration of many components. Micro-optical components are key elements for building compact optoelectronic systems and are well suited for integration with other devices. Another area where micro-optical elements can play an important role is the use of lasers in medicine, industrial machining, metrology, etc. In most cases, the laser beam characteristic is not directly suited for the application and external optics is needed to focus, shape or split the laser beam.</p><p>In the first part of this thesis, the fabrication of continuous-relief diffractive optical elements, such as diffractive lenses and blazed gratings, in GaAs is examined. The manufacturing technology uses electron-beam lithography followed by plasma etching in an inductively coupled plasma etching system. In the next step, these diffractive elements were monolithically integrated with vertical-cavity surface-emitting lasers.</p><p>In the second part of this thesis a novel topic is examined, diamond micro-optics. Diamond is a unique material in many aspects, it is the hardest material mankind knows, it has an extremely wide optical transmission window, and it possesses the highest thermal conductivity of all solids. Until today, due to difficulties in machining diamond, the realization of diamond optics has been limited. By using the same technology we earlier developed for the fabrication of GaAs optics we demonstrate for the first time continuous-relief structures in diamond of optical quality. Several diamond micro-optical structures are presented; sub-wavelength gratings for reduction of unwanted Fresnel reflections, diffractive fan-out elements used to split a CO₂-laser beam and refractive microlens arrays.</p><p>The accuracy of the fabrication process by plasma etching was evaluated by optical and topographical measurements, in all cases the optical components were of very high quality. </p>

<p>Die casting is a very cost-efficient method of forming thin-walled and complex near net-shaped products with close geometric tolerances and good surface finish. A permanent die tool is used to make large quantities of identical products. The performance and tool life are limited by several mechanisms, e.g. thermal fatigue cracking, erosion, and corrosion. To develop new and more resistant tool materials for die casting detailed knowledge of the actual casting conditions and the tool failure mechanisms are essential. This thesis contributes to an increased knowledge of tool failure in die casting by investigating and simulating actual casting conditions and tool failure mechanisms.</p><p>A method to record the temperature fluctuations in a cavity insert during actual brass die casting was developed, and details of the temperature conditions were obtained. Also, a test method based on cyclic induction heating and internal cooling of hollow cylindrical test rods was developed, where the surface strain during thermal cycling could be measured. This method reproduced the characteristic type of surface cracking observed on die casting tools, and proved to give information of the strains and stresses behind the fatigue failure.</p><p>In actual die casting, the dominant tool failure mechanism is thermal fatigue cracking. The formation of the cracks is associated to accumulation of the local plastic strain that occurs during each casting cycle. Initial crack growth is facilitated by oxidation of the crack surfaces, and proceeded growth is facilitated by this oxidation in combination with crack filling of cast material, and by softening of the tool material. In addition, local enrichment of Pb at the crack front from the cast alloy melt was also observed to promote the crack growth in die casting of brass.</p><p>In an investigation of thermal fatigue of two hot work tool steels, quenched and tempered to different conditions, it was found that low-cycle fatigue occurs, although the estimated tensile stress never exceed the initial yield strength of the steel. The reason is a gradual softening of the steel during the thermal cycling, and the presence of stress raising defects. The resistance against thermal cracking improves with initial tool steel hardness, because any initial ranking in hardness among the steels is unaffected by the thermal cycling.</p><p>Another investigation on a selection of surface engineered tool steels, including common diffusion treatments, PVD coatings and combinations of these, showed that surface engineering generally reduce the resistance against thermal cracking as compared to untreated references, since the engineering processes influence negatively on the mechanical properties of the hot work tool steels.</p><p>Finally, corrosion tests of CrN PVD-coated tool steels by exposing them to molten aluminium revealed the mechanisms of initiation and progress of liquid metal corrosion of this material combination, and that the corrosion resistance improves with the CrN coating thickness.</p>

<p>Microfluidics can be used to increase performance, reduce reagent consumption and increase throughput in chemical analysis. With the forthcoming development of more advanced microfluidic systems, the integration of actuating elements becomes essential, giving the ability to control and manipulate fluid flow as well as sample or other components. This thesis addresses miniaturisation of piezoceramic actuators, in particular important technological issues when actuators are integrated in microfluidic systems. Thick film multilayer fabrication technology for piezo­ceramics has been further developed, e.g. by introducing techniques for integration of microfabricated channel structures and via interconnects in multilayer components. New building techniques have been incorporated to allow miniaturisation of devices. A rapid prototyping technique for advanced multilayer actuators based on mechanical machining has also been developed and used in subsequent work.</p><p>When interfacing the macro and the micro world in miniaturised chemical analysis systems, non-contact sample dispensing methods such as ink-jet technology are needed. Thus a piezoactuated flow-through microdispenser, suitable for high-speed on-line chemical sample handling has been investigated. A new miniaturised actuator has been developed and integrated in the microdispenser, simplifying assembly and demonstrating an improved performance of the device.</p><p>With the prospect of performing automated and highly parallel analysis in reusable microarray devices, a new concept for dynamic arraying is presented. Non-contact trapping of particle or bead clusters in a microfluidic system is demonstrated utilising acoustic radiation forces in standing ultrasonic waves. The integration of piezoceramic micro­transducers has been shown to render possible localised and spatially controlled trapping of individually addressable particle clusters in micro­fluidics. The importance of the acoustic near field in miniaturised devices has been identified and utilised to give strong trapping forces. By making use of disposable chemically activated microbead arrays within a flow-through device, a flexible system is emerging with e.g. applications in proteomics.</p>