<p>The high pressure and high temperature (HPHT) behavior of Ti_1-xAl_xN coatings on cutting tool inserts have been of interest for this diploma work. A literature study of HPHT techniques as well as measurement methods has been done. A diamond anvil cell (DAC) would be a good device to achieve high pressure and high temperature conditions on small samples. Another way to obtain these conditions would be a cutting test, which has been performed on a Ti_1-xAl_xN coated cutting tool insert with x = 0.67. Also a cubic press could be used to apply HPHT on a     Ti_1-xAl_xN sample or a large volume press on a whole cutting tool insert. To measure hardness on thin coatings a nanoindentor could be used, which have been done on heat-treated Ti_0.33Al_0.67N and TiN samples. X-ray diffraction (XRD) is a suitable method to measure phase composition of a sample and was performed on the cutting tested insert as well as on an untreated reference insert. Three ways to continue this project have been outlined all starting with more comprehensive cutting tests.</p>

Instrumented nanoindentation techniques have been widely used in characterizing mechanical behavior of materials in small length scales. For defect-free single crystals under nanoindentation, the onset of elastic-plastic transition is often shown by a sudden displacement burst in the measured load-displacement curve. It is believed to result from the homogeneous dislocation nucleation because the maximum shear stress at the pop-in load approaches the theoretical strength of the material and because statistical measurements agree with a thermally activated process of homogeneous dislocation nucleation. For single crystals with defects, the pop-in is believed to result from the sudden motion of pre-existing dislocations or heterogeneous dislocation nucleation. If the sample is prestrained before nanoindentation tests, a monotonic decrease of the measured pop-in load with respect to the increase of prestrain on Ni and Mo single crystals is observed. A similar trend is also observed that the pop-in load will gradually decrease if the size of indenter tip radius increases. This dissertation presents a systematic modeling endeavor of energetics and kinetics of defect initiation in the stressed volume at small scales. For homogeneous dislocation nucleation, an indentation Schmid factor is determined as the ratio of maximum resolved shear stress to the maximum contact pressure. The orientation-depended nanoindentation pop-in loads are predicted based on the indentation Schmid factor, theoretical strength of the material, indenter radius, and the effective indentation modulus. A good agreement has been reached when comparing the experimental data of nanoindentation tests on NiAl, Mo, and Ni, with different loading orientations to theoretical predictions. Statistical measurements generally confirm the thermal activation model of homogeneous dislocation nucleation, because the extracted dependence of activation energy on resolved shear stress is almost unique for all the indentation directions. For pop-in due to pre-existing defects, the pop-in load is predicted to be dependent on the defect density and the critical strength for heterogeneous dislocation nucleation. The cumulative probability of pop-in loads contains convoluted information from the homogenous dislocation nucleation, which is sensitive to temperature and loading rate, and heterogeneous dislocation nucleation due to the unstable change of existing defect network, which is sensitive to the initial defect distribution.

The high pressure and high temperature (HPHT) behavior of Ti1-xAlxN coatings on cutting tool inserts have been of interest for this diploma work. A literature study of HPHT techniques as well as measurement methods has been done. A diamond anvil cell (DAC) would be a good device to achieve high pressure and high temperature conditions on small samples. Another way to obtain these conditions would be a cutting test, which has been performed on a Ti1-xAlxN coated cutting tool insert with x = 0.67. Also a cubic press could be used to apply HPHT on a     Ti1-xAlxN sample or a large volume press on a whole cutting tool insert. To measure hardness on thin coatings a nanoindentor could be used, which have been done on heat-treated Ti0.33Al0.67N and TiN samples. X-ray diffraction (XRD) is a suitable method to measure phase composition of a sample and was performed on the cutting tested insert as well as on an untreated reference insert. Three ways to continue this project have been outlined all starting with more comprehensive cutting tests.

With the recent development of in situ transmission electron microscopy (TEM) characterization techniques, the real time study of property-structure correlations in nanomaterials becomes possible. This dissertation reports the direct observations of deformation behavior of Al2O3-ZrO2-MgAl2O4 (AZM) bulk ceramic nanocomposites, strengthening mechanism of twins in YBa2Cu3O7-x (YBCO) thin film, work hardening event in nanocrystalline nickel and deformation of 2wt% Al doped ZnO (AZO) thin film with nanorod structures using the in situ TEM nanoindentation tool. The combined in situ movies with quantitative loading-unloading curves reveal the deformation mechanism of the above nanomaterial systems. At room temperature, in situ dynamic deformation studies show that the AZM nanocomposites undergo the deformation mainly through the grain-boundary sliding and rotation of small grains, i.e., ZrO2 grains, and some of the large grains, i.e., MgAl2O4 grains. We observed both plastic and elastic deformations in different sample regions in these multi-phase ceramic nanocomposites at room temperature. Both ex situ (conventional) and in situ nanoindentation were conducted to reveal the deformation of YBCO films from the directions perpendicular and parallel to the twin interfaces. Hardness measured perpendicular to twin interfaces is ~50% and 40% higher than that measured parallel to twin interfaces, by ex situ and in situ, respectively. By using an in situ nanoindentation tool inside TEM, dynamic work hardening event in nanocrystalline nickel was directly observed. During stain hardening stage, abundant Lomer-Cottrell (L-C) locks formed both within nanograins and against twin boundaries. Two major mechanisms were identified during interactions between L-C locks and twin boundaries. Quantitative nanoindentation experiments recorded during in situ experiments show an increase of yield strength from 1.64 to 2.29 GPa during multiple loading-unloading cycles. In situ TEM nanoindentation has been conducted to explore the size dependent deformation behavior of two different types (type I: ~ 0.51 of width/length ratio and type II: ~ 088 ratio) of AZO nanorods. During the indentation on type I nanord structure, annihilation of defects has been observed which is caused by limitation of the defect activities by relatively small size of the width. On the other hand, type II nanorod shows dislocation activities which enhanced the grain rotation under the external force applied on more isotropic direction through type II nanorod.

Ultra-high performance concrete (UHPC) is relatively a new generation of concretes optimized at the nano and micro-scales to provide superior mechanical and durability properties compared to conventional and high performance concretes. Improvements in UHPC are achieved through: limiting the water-to-cementitious materials ratio (i.e., w/cm < 0.20), optimizing particle packing, eliminating coarse aggregate, using specialized materials, and implementing high temperature and high pressure curing regimes. In addition, and randomly dispersed and short fibers are typically added to enhance the material¡¦s tensile and flexural strength, ductility, and toughness. There is a specific interest in using UHPC for precast prestressed bridge girders because it has the potential to reduce maintenance costs associated with steel and conventional concrete girders, replace functionally obsolete or structurally deficient steel girders without increasing the weight or the depth of the girder, and increase bridge durability to between 75 and 100 years. UHPC girder construction differs from that of conventional reinforced concrete in that UHPC may not need transverse reinforcement due to the high tensile and shear strengths of the material. Before bridge designers specify such girders without using shear reinforcement, the long-term tensile performance of the material must be characterized. This multi-scale study provided new data and understanding of the long-term tensile performance of UHPC by assessing the effect of thermal treatment, fiber content, and stress level on the tensile creep in a large-scale study, and by characterizing the fiber-cementitious matrix interface at different curing regimes through nanoindentation and scanning electron microscopy (SEM) in a nano/micro-scale study. Tensile creep of UHPC was more sensitive to investigated parameters than tensile strength. Thermal treatment decreased tensile creep by about 60% after 1 year. Results suggested the possibility of achieving satisfactory microstructural refinement at the same temperature input despite the maximum temperature applied. For the first time, the presence of a 10 Ým (394 micro inch) wide porous fiber-cementitious matrix interface was demonstrated by nanoindentation and SEM for non-thermally treated UHPC only. Tensile creep at 90 days increased by 64% and 46% upon eliminating fibers for thermally and non-thermally treated UHPC, respectively. Increases in creep upon reducing the fiber content suggested that fibers carry part of the sustained load and thus reduce creep. Tensile creep strain was proportional to the stress applied up to 60% of the ultimate strength. No tensile creep failure occurred for a period of 1 year for pre-cracked UHPC under stress level of 40%. Also, no tensile creep failure occurred for a period of 90 days under stress level of 60%. Tensile creep failure occurred at stress levels of 70% and 80%. This study showed that fibers cannot be accounted for as shear reinforcement in lieu of stirrups unless micro-defect-free fiber-matrix interface is achieved.

Combustion chemical vapor deposition (combustion CVD) is a thin film deposition process that uses a flame created by the ignition of an aerosol containing precursors dissolved in a flammable solvent. Combustion CVD is a relatively new technique for creating thin film oxide coatings. Combustion CVD has been successfully used to deposit high quality thin oxide films for potential applications such as thermal barrier coatings, dielectric thin films, composite interlayer coatings, etc. The present work involved developing the optimum parameters for deposition of thin films of yttria-stabilized zirconia (YSZ), alumina (Al₂O₃), and YSZ-alumina composites followed by a determination of the mechanical properties of the films (measured using nanoindentation) as a function of composition. The optimized parameters for deposition of YSZ, alumina, and YSZ-alumina composites onto single crystal a-plane alumina involved using an organic liquid as the flammable solvent and Y 2-ethylhexanoate, Zr 2-ethylhexanoate and Al acetylacetonate as the metal precursors at a 0.002 M concentration delivered at 4 ml/min at flame temperatures of 155 ℃ and substrate temperatures of 105 ℃. The resulting films were grown with deposition rates of ~ 1.5 μm/hr. Measurement of the mechanical properties (hardness, elastic modulus and fracture toughness) of the films was performed using a mechanical properties microprobe called the Nanoindenter®. In order to obtain valid results from nanoindentation, the combustion CVD films were optimized for minimum surface roughness and grown to a thickness of approximately 0.8 μm. With the penetration depth of the indenter at approximately 150 nm, the 800 nm thickness of the film made influences of the substrate on the measurements negligible. The hardnesses and elastic moduli of the YSZ-alumina films did not vary with the composition of the film. The fracture toughness, however, did show a dependence on the composition. It was found that second phase particles of alumina grown into a YSZ matrix increased the fracture toughness of the films (on average, 1.76 MPa• m⁰.⁵ for 100% YSZ to 2.49 MPa• m⁰.⁵ for 70 mol% YSZ/30 mol% alumina). Similarly, second phase particles of YSZ grown into an alumina matrix also increased the fracture toughness (on average, 2.20 MPa• m⁰.⁵ for 100% alumina to 2.45 MPa• m⁰.⁵ for 37.2 mol% YSZ/62.8 mol% alumina). Modeling of the fracture toughness of the YSZ-alumina films was successfully achieved by using the following toughening mechanisms: crack deflection from the second phase particles, grain bridging around the particles, and residual stress from the CTE mismatch between the film and the substrate and between the second phase particles and the matrix of the film.

Most of the surfaces have roughness down to atomic scales. When two surfaces come into contact, the nature of the roughness determines the properties like friction and wear. Analysis of the rough surface contacts is always complicated by the interaction between the material size effects and the micro-geometry. Contact mechanics could be simplified by decoupling these two effects by magnifying the scale of roughness profile. Also, tailoring the roughness at different scale could show a way to control the friction and wear through surface micro-structure modifications. In this work, the mechanics of contact between a rigid, hard sphere and a surface with a well defined roughness profile is studied through experiments and finite element simulation. The well defined roughness profile is made up of a regular array of pyramidal asperities. This choice of this geometry was mainly dictated by the fabrication processes. The specimens were made out of an aluminium alloy (6351-T6) such that there could be a direct application of the results in controlling the tribological properties during aluminium forming. Experiments on the pyramidal aluminium surface is carried out in a 250 kN Universal Testing Machine (INSTRON 8502 system) using a depth sensing indentation setup. A strain gauge based load cell is used to measure the force of the indentation and a LVDT (Linear Variable Differential Transformer) is used to measure the penetration depth. The load and the displacement were continuously recorded using a data acquisition system. A 3-D finite element framework for studying the elastic-plastic contact of the rough surfaces has been developed with the commercial package (ABAQUS). Systematic studies of indentation were carried out in order to validate the simulations with the experimental observations. The simulation of indentation of flat surface is carried out using the implicit/standard (Backward Euler) procedure, whereas, the explicit finite element method (Forward Euler) is used for simulating rough surface indentation. It is found that the load versus displacement curves obtained from experiments match well with the finite element results (except for the error involved in determining the initial contact point). At indentation depths higher than a value that is determined mainly by the asperity height, the load-displacement characteristics are similar to that pertaining to indentation of a flat, smooth surface. From the finite element results, it is found that at this point, the elastic-plastic boundary is more or less hemispherical as in the case of smooth surface indentation. For certain geometries, it is found that there could exist an elastic island in the sub-surface surrounded by plastically deformed material. This could have interesting applications.

In the last half of the XX century and the first years of the XXI century a large amount of methods for the determination of mechanical and tribological properties of materials on the micro- and nano-scale were developed. However, some problems and disadvantages are kept up to now. The combined application of normal and lateral forces allows to extend the possibilities of conventional contact mechanical approaches for investigations of mechanical and tribological behaviour of bulk and coated materials. Due to the unique construction of the Lateral Force Unit (LFU) the lateral force can be applied to the sample during normal indentation by the commercial nanoindenter UMIS 2000. Thus, the presented thesis reports the detailed study of the LFU capabilities for the determination of mechanical properties and tribological behavior on the micro-scale. At first it was found that the most appropriate standard position for the correct combined application of normal and lateral forces is the LFU inclination by 3.3° with respect to the UMIS stage. This standard position allows to minimize the influence of different factors on the measuring process. It was shown that the shape of normal displacement-time curves is the most convenient after the thermal drift correction for the simplification of the determination of such parameters as the maximal normal displacement and the residual normal deformation obtained by lateral force application. It was found that the crack formation can be detected as the observation of sudden change of lateral displacement in lateral force-displacement curve together with normal displacement in normal displacement-time curve. These investigations were performed for single-crystal sapphire. For the first time the crack in single-crystal sapphire was detected by the contact mechanical method in situ. The critical tensile stress for the crack formation in single-crystal sapphire was determined as 9.68+-0.22 GPa. It was established that the onset of plastic deformation can be detected by the observation of shape change of lateral force-displacement curve together with the appearance of residual normal deformation in normal displacement-time curve. These investigations were done for bulk BK7 glass and silicon dioxide film with thickness of 951 nm on silicon substrate. The yield strength for the silicon dioxide film was evaluated as 6.83+-0.02 GPa. It was found that the static friction of materials couples can be evaluated by the analysis of lateral force-displacement curves with the error of 5-10 %. The static friction coefficients for fused silica, BK7 glass, single-crystal sapphire as well as SiO2, DLC and CrN0.08 coatings were determined against diamond, tungsten carbide and sapphire spherical indenter with different radii. The effect of normal load on static friction for fused silica and BK7 glass against 10.5 µm diamond spherical indenter was also studied. It was found that the onset of plastic deformation leads to a significant change of static friction. / In der zweiten Hälfte des 20. Jahrhunderts und während den ersten Jahren des 21. Jahrhunderts wurden zahlreiche Methoden zur Untersuchung mechanischer und tribologischer Materialeigenschaften auf der Mikro- und Nanometerskala entwickelt. Trotz der Fortschritte auf diesem Gebiet blieben vielfältige Fragestellungen unbeantwortet oder waren mit den vorhandenen experimentellen Untersuchungsmethoden nicht zugänglich. Mit der kombinierten Belastung aus Lateral- und Normalkräften wurden die etablierten Messverfahren um einen viel versprechenden Ansatz zur Charakterisierung mechanischer sowie tribologischer Eigenschaften erweitert, der sowohl für Massiv- als auch Schichtmaterialien anwendbar ist. Die einzigartige Konstruktion einer Lateralkrafteinheit bietet als separates Bauteil die Möglichkeit während eines Standardeindringversuches mittels des kommerziellen Nanoindenters UMIS 2000 bei normaler Last, eine laterale Belastung zu überlagern. Die vorliegende Arbeit zeigt eine detaillierte Studie der Einsatzmöglichkeiten der Lateralkrafteinheit hinsichtlich der Charakterisierung mechanischer Eigenschaften und tribologischen Materialverhaltens auf der Mikrometerskala. Zunächst wurde herausgefunden, dass eine Verkippung der Lateralkrafteinheit von 3,3° gegenüber dem UMIS-Rahmen notwendig ist, um eine hochgenaue und definierte Belastung aus lateraler und normaler Kraft auf die Probe auszuüben. Mit dieser durchgeführten Korrektur der Ausrichtung gelang es weitere auf den Messprozess einwirkende Effekte zu minimieren. Nach der Korrektur der thermischen Drift scheinen die gemessenen Normalverschiebungs-Zeit-Kurven für die Bestimmung von mechanischen Parametern wie maximaler Verschiebung oder bleibender Eindrucktiefe bei lateraler Belastung geeignet zu sein. Als ein weiteres Ergebnis gelang es, durch die kombinierte Belastung der Kraftkomponenten Bruchversagen nachzuweisen. Das Materialversagen wurde durch eine abrupte Änderung der lateralen Verschiebung im Last-Verschiebungs-Diagramm angezeigt. Mit dieser Methode wurde erstmalig in-situ das Bruchversagen am Beispiel des einkristallinen Saphirs detektiert. Die kritische Zugspannung, die zur Bruchbildung bei Saphir führte, war 9,68+-0,22 GPa. Die Analyse der Kurvenform der Kraft-Verschiebungs-Kurven für die Lateralbelastung im Zusammenhang mit dem Auftreten von bleibender Deformation in den zugehörigen Verschiebungs-Zeit-Kurven der normalen Belastung liefert den Beginn der plastischen Deformation. Massive BK7-Glasproben sowie SiO2-Schichten wurden untersucht. Für die Fließspannung der SiO2-Schicht wurde ein Wert von 6,83+-0,02 GPa ermittelt. Der Haftreibungskoeffizient für verschiedene Materialpaarungen wurde aus den Last-Verschiebungs-Kurven mit einer Genauigkeit von 5-10 % berechnet. Zu den untersuchten Materialien gehörten Quarz, einkristallines Saphir, BK7-Glas sowie SiO2-, DLC- und CrN0.08-Schichten, die mit Diamant, Wolframkarbid und Saphir-Indentern gepaart wurden. Zusätzlich wurde der Einfluss der Normallast auf den Haftreibungskoeffizienten für Quarz und BK7-Glas gegen Diamant studiert. Es zeigte sich, dass der Beginn der plastischen Deformation zu signifikanten Änderungen der Haftreibung führt.

Nanoindentations-Messungen haben in den letzten Jahrzehnten als Verfahren zur Ermittlung mechanischer Eigenschaften dünner Schichten stark an Bedeutung gewonnen. Für die Gewinnung eines tiefergreifenden Verständnisses des mechanischen Verhaltens dieser Schichten ist die Kenntnis des Elastizitätsmoduls und der Fließgrenze von essentieller Bedeutung – nicht zuletzt, da diese auch als Eingabeparameter für Simulationen des Materialverhaltens gefordert sind. Eine noch nicht im Detail verstandene Forschungsfrage bei der Kennwertermittlung ist die Berücksichtigung des Dünnschichtcharakters der Proben, deretwegen diese Untersuchungen im Wesentlichen immer noch einen Grundlagencharakter tragen und derzeit Gegenstand intensiver weltweiter Forschung sind. Auswege für eine solche Berücksichtigung existieren bisher nur für wenige Anwendungsfälle. Das Konzept des effektiven Indenters stellt eine Erweiterung der Auswerteansätze und damit neue Möglichkeit für die mechanische Charakterisierung der Dünnschichteigenschaften dar. In der vorliegenden Arbeit wird untersucht, inwieweit dieses Konzept zur Ermittlung des Elastizitätsmoduls dünner Schichten geeignet ist. Ebenso werden die Untersuchungen auf die Fließgrenze ausgeweitet. Beispielhaft kommen unterschiedliche Schichtmaterialien zum Einsatz, mit denen der Unterschied zwischen den Schicht-Substrat-Eigenschaften – Elastizitätsmodul und Fließgrenze – variiert werden kann. Durch Vergleich der für die BERKOVICH-Eindrücke erhaltenen Ergebnisse zu den mittels der Kugeleindrucksversuche bestimmten Werte – als etabliertes Messverfahren – wird festgestellt, dass o. g. Konzept prinzipiell für die oben angeführten Fragestellungen geeignet ist, insofern die erreichten Eindringtiefen im Vergleich zur Schichtdicke relativ gering sind. Physikalische Ursachen für dieses Verhalten werden vorgeschlagen und diskutiert. Ebenso wird eine spezielle Vorgehensweise des Konzepts des effektiven Indenters für die Charakterisierung von porösen sowie nichtporösen Low-k-Schichtmaterialien untersucht. Zusätzlich werden Finite-Elemente-Simulationen für grundlegende Betrachtungen zur Wirkungsweise des o. g. Konzepts anhand von massiven Proben herangezogen. / Considerable research effort has focused on measuring the mechanical properties of thin films via nanoindentation. To characterize the mechanical behavior of thin films, accurate determination of Young’s modulus and yield strength is required. For the purpose of modeling and dimensioning, these quantities serve as input parameters as well. An existing major challenge in the context of (nanoindentation) data analysis is the complete consideration of the layered structure of the specimen. In the literature, a few experimental and theoretical-based approaches have been developed to extract actual film properties. However, those approaches are only applicable under specific conditions and, hence, the problem is not satisfyingly solved to date. Therewith, investigations of accurately assessing mechanical properties of thin films, in general, or Young’s modulus and yield strength, in detail, are still part of ongoing research in the field of mechanical testing in materials research and development. The concept of the “effective indenter” is an extension of the current and established analysis of nanoindentation data and is a new possibility to determine mechanical properties of thin films. In this work, an investigation is given concerning the suitability of the model, in a specific approximation, for determining Young’s modulus of thin films. In a second step, the investigations are focused on the determination of yield strength. Film/substrate composites having a varying ratio of modulus and yield strength between film and substrate are chosen; BERKOVICH indentations are analyzed and spherical indentation experiments are used as second and independent technique. It is shown that the model is suitable to deliver Young’s modulus of thin films. However, a critical ratio of indentation depth to film thickness is identified; for ratios above this critical value, the model, in the present approximation, can no longer be used. Physical mechanisms that explain this finding are suggested and discussed. Moreover, the above-mentioned model is used to characterize the very specific class of materials of non-porous and porous low-k dielectric thin films in terms of yield strength and Young’s modulus. Finally, finite element modeling is used to study critical issues in applying the model of the “effective indenter” and its specific approximation used here for analysis of nanoindentation data for bulk materials.

Die Herstellung von Kompositschichten aus unterschiedlichen Materialien mit verbesserten Schichteigenschaften stellt einen in den letzten Jahren intensiv erforschten Bereich der Dünnschichttechnik dar. Eine Methode zur Präparation solcher Kompositschichten besteht darin, Nano- oder Mikropartikel in eine Matrix aus einem anderen Material einzubringen. In der vorliegenden Arbeit werden so bis zu einige Mikrometer dicke Kompositschichten untersucht, die mit einem Sol-Gel-Verfahren hergestellt wurden und die bis zu 30 Gew.-% Wolframdisulfid-Partikel enthalten, welche als anorganische Fullerene typische Teilchengrößen von etwa 100 nm bis 200 nm aufweisen. Zwei unterschiedliche Arten an Kompositschichten mit eingebetteten Partikeln aus Wolframdisulfid werden hergestellt: Zum einen Schichten mit einer deutlich steiferen Matrix aus Aluminiumoxid und zum anderen Schichten mit einer Matrix aus organisch modifiziertem Siliziumoxid. Die strukturelle Charakterisierung der Schichten erfolgt über verschiedene analytische Verfahren. So werden die Kristallstruktur und chemische Zusammensetzung der Schichten mit Hilfe von Röntgenbeugungs- und Röntgenfluoreszenzmessungen sowie energiedispersiver Röntgenspektroskopie ermittelt. Raster- und Transmissionselektronenmikroskopie werden verwendet, um Aufschluss über die Verteilung der Wolframdisulfid-Partikel und ihren Einschluss in die jeweilige Matrix zu erhalten. Weiterhin werden die Rauheit und das Versagen der Schichthaftung auf dem Substrat untersucht. Der Einfluss der inkorporierten Partikel sowie der Herstellungstemperatur der Proben auf die mechanischen Eigenschaften der Kompositschichten wie Härte und E-Modul werden experimentell mit Nanoindentationsmessungen sowie theoretisch mittels verschiedener Modelle für effektive Materialien ermittelt. Schließlich erfolgt eine Charakterisierung der tribologischen Eigenschaften der Kompositschichten im Vergleich zu undotierten Schichten aus Aluminiumoxid oder organisch modifiziertem Siliziumoxid. Mit Hilfe einer Kugel-Scheibe-Geometrie wird der Reibkoeffizient der Schichten unter verschiedenen Bedingungen gemessen. Dabei zeigt sich, dass bei ausreichender Menge des eingeschlossenen Wolframdisulfids ein reibungsmindernder Effekt auftritt, was vielversprechend für eine mögliche Anwendung solcher Kompositschichten ist. / The preparation of composite coatings consisting of different materials with improved properties has been an intensively studied area of thin film technology in recent years. One method to prepare such composite coatings is the incorporation of nano or micro particles into a matrix of a different material. In this thesis, such composite coatings are investigated which have been prepared via a sol-gel route und contain up to about 30 wt.-% tungsten disulfide particles. These inorganic fullerenes have typical particle sizes of about 100 nm to 200 nm. Two different types of composite coatings with a thickness of up to a few micrometers and with embedded tungsten disulfide particles are prepared: First, coatings with a relatively stiff alumina matrix, and second, coatings with a matrix made of organically modified silica. Different analytical methods are used for the structural characterization of the coatings. The crystal structure and the chemical composition of the coatings are determined via x-ray diffraction and x-ray fluorescence measurements and via energy-dispersive x-ray spectroscopy. Through scanning and transmission electron microscopy the incorporation and the distribution of the tungsten disulfide particles in the respective matrix are analysed. Furthermore, the roughness and the adhesion of the coatings on the substrate are investigated. The influence of the embedded particles and of the temperature of the final heat treatment during the sample preparation on the mechanical properties, like elastic modulus and hardness, of the composite coatings are measured through nanoindentation testing. These experimental results are compared with theoretical values determined via different analytical models for effective materials. Finally, the tribological behavior of the composite coatings is investigated in comparison to pure coatings made of alumina or organically modified silica. With ball-on-disc tests the coefficient of friction of the coatings is measured under different conditions. It can be seen that the incorporation of a sufficiently high amount of tungsten disulfide leads to a strong reduction of friction, which is promising for a possible application of such composite coatings.