This thesis is focused on the study of changes in properties of the aqueous suspensions of corundum during ultrafine grinding without and with the addition of grinding activator. Such studies are an important step in  optimizing the grinding process properly, because by measuring physical properties of a particulate substance, it is easy to determine the actual fineness of the ground substance and its quality for further processing. For the measurement of granulometry, zeta potential, rheological behavior and turbidity, corundum suspensions in distilled water were prepared in a 1:5 ratio without the addition of grinding activator and with the addition of triethanolamine (TEA), by using a planetary mill. The suspensions showed pseudoplastic behavior and the zeta potential of all samples ranged between -30 and 30 mV, thus the suspensions were rather unstable. During the grinding, the viscosity and turbidity of the samples increased. TEA was not proved to be a suitable activator for wet milling of corundum because of higher degree of fineness achieved during milling without an activator.

Sri Lanka is one of the leading countries in export of high quality corundum (Al2O3) gemstones due to the Precambrian rocks geological background. Combined highgrade metamorphic silicates and carbonate rocks makes perfect conditions for crystallization of this mineral. Weathered and eroded rocks have been transported by fluvial processes and formed gem gravels that are located throughout the country but mainly in the Highland complex of Sri Lanka. In order to determine whether a gemstone is corundum or any other gem mineral different techniques and instrumental methods are used. This report focuses on instrumental methods used to measure the minerals physical properties in order to get a definite mineral identification. Mineral identification in gemological circles is critical for determining the commercial value of a specimen. Factors like transparency and color of and inclusions in gemstone have to be taken into account when evaluating the value of a specimen. It also needs to be distinguished from artificial gemstones and heattreated specimens that in recent years have become more common due to more advanced techniques. By examine inclusions and the chemical composition of a rough or facetted specimen the origin and process can be determined. / Sri Lanka är ett av de ledande exportländerna av högkvalitativ ädelkorund (Al2O3) som bildats i landets prekambriska bakgrund. Hög metamorfos av silikat- och karbonatrika bergarter har skapat rätt miljö för mineralet att bildas. Vittrad berggrund har transporterats och avsatts av fluviala processer och ädelstensförande grus finns i huvudsakligen i Sri Lankas Highlandkomplex. För att kunna avgöra om en ädelsten är korund eller ett annat mineral används olika tekniker och instrument. Denna rapport fokuserar huvudsakligen på instrumentella metoder som mäter fysikaliska egenskaper hos mineral för att därigenom kunna få en definitiv mineralidentifikation. Inom gemologi är det absolut nödvändigt med mineralidentifikation för att bestämma det kommersiella värdet av en ädelsten. Även faktorer som transparens, färg och inneslutningar hos en ädelsten måste undersökas vid värdering. Syntetiska och eller värmebehandlade ädelstenar har blivit allt mer vanliga genom utvecklig av avancerad teknik och att skilja dessa från naturliga stenar är också viktigt. Genom undersökning av inneslutningar och den kemiska sammansättningen av en ädelsten kan dess ursprung och i vissa fall de geologiska bildningsprocesserna fastställas.

Nichtwäßrige Sol-Gel-Vorstufen, die zu einem Mischgefüge aus Al2O3 und YAG führen (Volumenverhältnis 45 : 55), wurden zu Fasern versponnen, in unterschiedlichen Atmosphären pyrolysiert und abschließend gesintert. Die strukturelle Ent-wicklung während der Pyrolyse der Gel-Fasern wurde in Abhängigkeit von Pyrolysetemperatur (200-850 °C) und -atmosphäre beschrieben. Die Zusammenhänge zwischen den mittels der Pyrolyseparameter variierten amorphen Strukturen und dem daraus resultierenden Kristallisations- und Sinterverhalten sowie den mechanischen Fasereigenschaften wurden gezeigt. Die isotropen Gel-Fasern sind frei von Poren und weisen lokal regelmäßig angeordnete, organische Domänen mit mittleren Abständen von 2 nm innerhalb des anorganischen Matrixgerüsts auf. Während der Pyrolyse auftretende Strukturveränderungen hängen stark von der Atmosphäre und der Temperatur ab. In Luft- und Sauerstoffatmosphäre trat ab 600 °C innerhalb der Fasern lokal eine Kristallisation von YAG und Korund in Form kugeliger Bereiche auf, die zum Bruch der Fasern bereits während der Pyrolyse führten. Die Abgabe organischer Bestandteile erfolgte bei Pyrolyse in Stickstoff im wesentlichen zwischen 300 °C und 500 °C, blieb jedoch auch bei höheren Temperaturen unvollständig. In Wasserdampf-Atmosphäre kam es durch Hydrolysereaktionen zwischen 250 °C und 385 °C zu einer verbesserten Abgabe der organischen Bestandteile. Der Kohlenstoffgehalt sinkt bei 385 °C unter 2 Masse-%. Werden dem Wasserdampf saure Gase wie z.B. Stickoxide zugesetzt, wird um 200 °C die Hydrolyse und Abgabe der Organik zusätzlich verstärkt. Nach Pyrolyse in Stickstoff oder wasserhaltigen Atmosphären blieben die Fasern amorph. Bei Pyrolyse in Stickstoff war die Struktur der Fasern porenfrei, wobei die organischen Pyrolysatreste wie in den Gel-Fasern als regelmäßig angeordnete, isolierte Bereiche innerhalb einer anorganischen Matrix vorlagen. In Wasserdampf bildete sich ab 250 °C aus den organischen Domänen eine geordnete Porenstruktur, die sich mit ansteigender Temperatur vergröberte. Auch in der aus verdampfter Salpetersäure erzeugten Atmosphäre bildeten sich Poren. Die Porendurchmesser und spezifischen Oberflächen der Fasern blieben jedoch geringer als in reinem Wasserdampf. In dem anorganischen Matrixgerüst änderten sich durch die Pyrolyse die Koordinationsverhältnisse der Al-Ionen. Ausgehend von der mehrheitlich 6-fachen Koordination in den Gel-Fasern kam es zunehmend zur Umlagerung in die 4- und 5-fache Koordination. Bei Pyrolyse in reinem Wasserdampf war diese Koordinationsveränderung deutlich schwächer ausgeprägt als in Stickstoff oder der Atmosphäre aus verdampfter Salpetersäure. Während der Sinterung treten intermediär gamma-Al2O3 und hexagonales YAlO3 als metastabile Phasen vor der Kristallisation von YAG auf. Mit der Kristallisation von Korund schließt die Phasenbildung der Al2O3-YAG-Fasern je nach vorangegangener Pyrolysebehandlung zwischen 1275 °C und 1315 °C ab. Die Abweichungen in der Kristallisationstemperatur bzw. Keimbildungsdichte von Korund und im Sinterverhalten ließen sich auf die Unterschiede in den amorphen Strukturen der pyrolysierten Fasern zurückführen. Hohe Anteile 6-fach koordinierter Al-Ionen und eine zu hohen spezifischen Oberflächen führende, feine Porosität erwiesen sich als günstige Strukturmerkmale für pyrolysierte Fasern. Die dabei entstandenen feinkörnigen, homogenen Gefüge konnten dicht gesintert werden und hatten die höchsten Festigkeiten und E-Moduln. Kohlenstoffgehalte bis zu 2 Masse-% wirkten sich in den offenporigen Zwischenprodukten nicht negativ auf das Sinterverhalten aus. In dieser Arbeit wurde gezeigt, daß die Kristallisation der Sol-Gel-abgeleiteten Fasern und damit auch die Ausbildung der keramischen Gefüge in entscheidendem Maße von den Pyrolysebedingungen abhängen. Bei einheitlicher Synthese der Gel-Fasern lassen sich durch die Pyrolysebehandlung unterschiedliche Strukturen in den amorphen Zwischenprodukten einstellen, die durch ihre spezifisches Kristallisations- und Sinterverhalten zu unterschiedlichen keramischen Gefügen in den Fasern führen. Die Optimierung der Gefüge vorstufenabgeleiteter Keramiken durch Zusatz von Keimen ("Seeding") ist seit längerem bekannt. In Ergänzung dazu bietet die gezielte Wahl der Pyrolysebedingungen eine weitere Möglichkeit zur Steuerung der Gefügeausbildung in Sol-Gel-Keramiken. / Ceramic fibers of Al2O3-YAG composition (volume ratio 45 : 55) were prepared by spinning non-aqueous sol-gel precursors to fibers which were then pyrolyzed in various atmospheres and finally sintered. Structural development of the gel fibers upon pyrolysis at temperatures between 200 °C and 850 °C was described for different atmospheres. Variation of pyrolysis conditions lead to different amorphous structures. A correlation between the amorphous structures and their crystallization and sintering behavior as well as mechanical fiber properties could be established. The gel fibers have an isotropic, pore-free structure which is characterized by an inorganic matrix that contains organic domains in a locally ordered arrangement with mean distances of 2 nm. Alteration of this structure strongly depends on the type of atmosphere and temperature during pyrolysis. In air and oxygen above 600 °C local, spherulitic crystallization of YAG and corundum occurs within the fibers and leads to fracture of the fibers. In nitrogen, organic constituents are mainly removed between 300 and 500 °C, but residues remain even at higher temperatures. Water vapor hydrolyses organic constituents and enhances their release at 200-385 °C. Thus carbon contents drops below 2 wt.-% at 385 °C. Additional acceleration of hydrolysis at ~200 °C can be achieved by addition of acidic gases like nitric oxide to the moist atmosphere. The structure of fibers pyrolysed in nitrogen or moist atmospheres remains amorphous. After pyrolysis in nitrogen the fibers are pore-free and the organic residues still appear as locally ordered domains within an inorganic matrix. In water vapor from 250 °C on, the release of organics leads to the formation of ordered micropores that coarsen with further increasing temperature. In the atmosphere of evaporated nitric acid, pores form too, but pore sizes and specific surface areas of the fibers are lower than in pure water vapor. The coordination of Al-ions in the inorganic network is altered by pyrolysis. Gel fibers mainly contain 6-fold coordinated Al-ions. With increasing temperature a rearrangement of part of the octahedrally coordinated Al-ions to 4- and 5-fold coordination was observed. While this rearrangement was only weakly pronounced for fibers pyrolysed in water vapor, in nitrogen or the atmosphere that was derived from evaporated nitric acid a significantly higher proportion of 6-fold coordinated Al-ions rearranged to lower coordination numbers. During the sintering process gamma-Al2O3 and hexagonal YAlO3 are formed as intermediate metastable phases prior to the crystallization of YAG. Formation of crystalline phases in the Al2O3-YAG fibers completes with the crystallization of corundum at 1275 to 1315 °C depending on pyrolysis conditions. Differences in crystallization temperature and nucleation density of corundum were put down the structural features of pyrolysed, amorphous fibers. A high proportion of 6-fold coordinated Al-ions and a high specific surface caused by fine pores revealed as favorable characteristics of low corundum crystallization temperature and high nucleation density. Such fibers could be fully densified resulting in the highest strength and Young's moduli in the ceramic fibers. Carbon contents up to 2 wt.-% were not deleterious to the densification of pyrolysed fibers with an open porous structure. The results presented in this study show that crystallization and microstructural evolution of sol-gel derived ceramic fibers critically depend on pyrolysis conditions. Different amorphous structures that lead to altered ceramic microstructures can be obtained from uniformly synthesized gel fibers by variation of pyrolysis conditions. Seeding is a well known process for the microstructural optimization of precursor derived ceramics. As a supplement the choice of suitable pyrolysis conditions is a further tool for the microstructure control in sol-gel ceramics.

This work deals with the study of limestone and corundum dry milling using attritor-type stirred mill in a batch mode. There were stearin and polyethylene glycol used as surfactants and spherical shaped steel grinding elements used for the experimental part of the work. The main idea was to examine behavior of the selected grinding stock type within a long-term grinding forces exposure in selected conditions of ultrafine dry milling leading up to the submicron area. Characterization of samples was performed by laser granulometry, X-ray powder diffraction analysis, flame atomic absorption spectroscopy, objective color determination and electrokinetic potential measurement. Experimetaly measured data implies that in all cases there was a re-agglomeration of the grinding stock particles occurring, although in different stages of the disintegration process and in mutually various degree. The analysis results denote that a larger erosion of the crystal structures with the associated increase of the amorphous phase in the submicron particle size took place in the grinding stock.

The main goal of this thesis is to compare 5 chosen grinding wheels, that vary by the material and structure. The testing is done in the company SLB, spol. s r.o., using a grinder on the holes BDU 80, which is set to 6 different settings of the grinding cycle, defined by the letters A´, A, B, C, D and E. These settings vary by the cutting conditions and enable to compare the tested grinding wheels by 8 measured parameters of the surface quality of the grinded bearing orbits of outer rings of the SLB 84-74 bearings, that are described by the drawing documentation.

Diese Arbeit hatte es zum Ziel, eine neue und effiziente Affinitätsplattform für die Aufreinigung und Isolierung von Proteinen basierend auf nicht‐porösen und stabilen Korund‐Partikeln zu entwickeln. Das Rohmaterial wurde kovalent mit Proteinbindern modifiziert, um so die Isolierung spezieller Target‐Proteine aus komplexen biologischen Proben zu realisieren. Für die erste Modifizierungsschicht auf der Korundoberfläche wurden verschiedene Phosphonsäuren und Silane untersucht. Anschließend wurde der etablierte bifunktionale Crosslinker Glutaraldehyd mit dem biokompatibleren verzweigten Polyglycerol (PG) verglichen. Es konnte gezeigt werden, dass Polyglycerol eine hervorragende Alternative zu Glutaraldehyd darstellen kann. Für die angestrebte Anwendung als neues Tool für die Antikörperreinigung wurde humanes IgG mit Protein‐A‐funktionalisierten Korundpartikeln erfolgreich aus Humanplasma isoliert. Um das Anwendungsspektrum der neuen Korundmethode auszuweiten, wurde im zweiten Teil dieser Arbeit eine Affinitätsplattform für die Isolierung Polyhistidin‐getaggten Proteinen basierend auf Metallionen‐funktionalisiertem Korund entwickelt und angewendet. Hauptkriterien dieser Methodenentwicklung waren die schnelle, effiziente und ökonomische Aufreinigung rekombinanter Proteine aus bakteriellen Lysaten in einem säulenfreien Format. Als Modellsystem wurde Polyhistidin‐getaggtes Protein A/G (His6‐PAG) mit Rinderserumalbumin versetzt, was die Entwicklung eines optimierten Protokolls für die Isolierung rekombinanter Proteine ermöglichte. Im direkten Vergleich mit kommerziellen Ni‐NTA‐Agarose‐Beads zeigten die Korundpartikel höhere Proteinreinheiten. Abschließend konnte gezeigt werden, dass Zink eine ideale Alternative als Metallion darstellt, um etwaige Nachteile des Nickels in der Anwendung von Life‐Science‐Methoden zu umgehen und eine zukunftsträchtige Methode mit weiterem Potenzial zu realisieren. / This work aimed to develop and establish a novel efficient affinity platform for protein purification based on nonporous, stable, and easily available corundum powder. The material was functionalized covalently with protein binders to isolate and enrich specific proteins from complex biological matrices. Phosphonic acids and silanes were tested as the first modification layer. In the next step, the well‐known bifunctional crosslinker glutaraldehyde was compared with a more biocompatible, hyperbranched polyglycerol (PG). It could have been shown that oxidized polyglycerol is an excellent alternative to glutaraldehyde. Human IgG was purified with protein A functionalized corundum from crude human plasma for the initial purpose of antibody isolation. To broaden the application of functionalized corundum, a novel purification platform for the isolation of poly His‐tagged proteins based on metal‐ion‐functionalized corundum was established.The main goal of this approach was the efficient, economical, and fast purification of recombinant proteins in a column‐free format that can also easily be performed in moderately equipped laboratories. As a model system for method optimization, His‐tagged protein A/G (His6‐PAG), mixed with bovine serum albumin (BSA), was established leading to a purification protocol with minimal nonspecific binding by the variation of the imidazole content in the used binding and washing buffers. Corundum in direct comparison with standard Ni‐NTA agarose beads generated higher purities of isolated proteins. Finally, it was shown that zinc‐functionalized corundum is another efficient approach to circumvent potential negative effects of nickel use in life science applications.

In this diploma thesis was analysed layer of corroded material created on refractory lining of reactors for mazut gasification. Samples of corroded material were analysed for SiO2, Al2O3, ZrO2, Fe2O3 a TiO2. Corroded material was further analysed by x-ray and IR spectroscopy to acquire more precise data about chemical composition. This thesis studies the exact effect of microstructure on static corrosion kinetics in system SiO2-Al2O3.

Diploma thesis deals with the research of oxide interphase of ceramic composite in dependence on the amount of precursor used in sol – gel method for deposition of titanium dioxide thin layer on corundum.

The aim of this thesis is to summarize the knowledge gained in the field of grinding medium-hard and hard materials. Work has focused on examining the grindability of the material using available laboratory mill. The part of the work is subsequent optimization of the grinding process on the device and evaluation of the results.

In order to considerably improve the quality of steel products, efforts are being made to increase the cleanness of steel. It is known that the size, type and distribution of non-metallic inclusions (NMIs) in metals significantly influence their mechanical properties. Within the frame of the Collaborativ Research Centre 920 'Multifunc-tional filters for metal melt filtration – a contribution to zero defect materials.”, carbon-bonded alumina filters for steel melt filtration has been investigated. In the present thesis, the interactions between coated carbon-bonded alumina filters and a steel melt were investigated in more detail, with the porous coatings being based on alumina. The time-depended behaviour was evaluated by immersing coated filters for different dwell times. After the immersion tests, the microstructure of the filter surface and the NMIs remaining in the solidified steel were examined to comprehend the interactions. The here presented results imply that carbon of the carbon-bonded alumina sub-strate took part in the filter–steel interactions. The presence of dissolved carbon at the filter–steel melt interface is essential to promote alumina dissolution and pre-cipitation processes. Thereby, the melt was locally supersaturated with aluminium, which reacted with dissolved oxygen to form secondary corundum. During these interactions, a liquid oxide film was formed directly at the ceramic surface and provided nuclei for heterogeneous nucleation of secondary corundum. After immersion during cooling, a characteristic layer built-up formed at the filters surface. All alumina-based coated filters contributed to the filtration of especially alumina-based NMIs, and outperformed the uncoated carbon-bonded alumina filter. During the first experimental trials, it became obvious that the thermal shock resistance of the alumina coating has to be enhanced. For this purpose, a material combination was investigated which so far has not been used as a coating material to the author’s knowledge: alumina-zirconia-titania in the ration 95 : 2.5 : 2.5. This material is known for its excellent thermal shock resistance. Thereby, the influence of zirconia or titania doping of the coating were considered. The addition of titania enhanced wetting of this filter by the steel melt. As a result, alumina inclusions of the steel melt were modified: they were more in number, but distinctly smaller compared to trials without filter or the immersion of the other filter types. Especially, the decreased average area of the alumina inclusions is interesting because the particle size of NMIs strongly influences the fatigue life of a steel product. The deformability of a steel product, however, is determined by the amount of NMIs. Thus, the modification of alumina inclusions by adding titania to the filter coating might present a way to tailor these inclusions depending on the product’s application.