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Der rasant fortschreitende Bodenverbrauch und die damit verbundene Bodenversiegelung in Österreich stellen für die Menschen mittel- bis langfristig eine existenzielle Bedrohung dar. Der Bodenverbrauch sollte daher rasch und dauerhaft auf ein vertretbares Maß gesenkt werden. Die hierfür zur Verfügung stehenden raumplanerischen Instrumente und Maßnahmen zeigen keine ausreichende Wirkung. Ein Mittel zum Flächensparen, dem bislang – v.a. in vorstädtischen und ländlichen Gebieten – (zu) wenig Beachtung geschenkt wird, ist bauliche Verdichtung. In der vorliegenden Diplomarbeit wird mithilfe einer Literaturrecherche, einer Analyse einschlägiger Rechtsnormen und mehrerer leitfadengestützter Expert:inneninterviews untersucht, wie auch in diesen Gebieten eine maßvolle, aber deutliche bauliche Verdichtung erzielt werden kann, die eine signifikante Reduktion des Bodenverbrauchs mit sich bringt. Der Fokus liegt dabei auf verpflichtenden Mindestbebauungsdichten als mit Abstand wichtigster Maßnahme zur Erreichung dieses Ziels. Das Kernstück der Arbeit bildet ein vom Verfasser entwickeltes Modell für verpflichtende Mindestbebauungsdichten, das sich in allen Bundesländern Österreichs umsetzen lässt. Dieses Modell sieht vor, dass sämtliche Gemeinden per Gesetz dazu verpflichtet werden sollten, für alle Grundstücke, die eine Widmung für Wohnzwecke aufweisen, standortangemessene Mindestdichten der Bebauung – d.h. Untergrenzen der zulässigen baulichen Dichte – rechtsverbindlich festzulegen, die grundsätzlich sowohl beim Neubau von Gebäuden als auch bei baulichen Veränderungen an Bestandsbauten zu erreichen sein sollten. Dadurch sollen v.a. freistehende Einfamilienhäuser in ihrer herkömmlichen – besonders flächenintensiven – Form zum Auslaufmodell werden., The rapidly increasing land consumption and the associated soil sealing in Austria pose an existential threat to people in the medium to long term. Land consumption should therefore be reduced to an acceptable level quickly and permanently. The instruments and measures offered by spatial planning to contain land consumption have not shown sufficient effect yet. A means to reduce land consumption is building densification. However, in suburban and rural areas, in particular, (too) little attention has been paid to this means so far. This diploma thesis investigates how a moderate, but still considerable building densification can be achieved even in these areas that leads to a significant reduction in land consumption. The investigation is based on a literature review, an in-depth analysis of relevant legal norms and several semi-structured interviews with architects and spatial planners. The focus is on mandatory minimum building densities, which are considered by far the most important measure to achieve this goal. The core of this thesis is a model for mandatory minimum building densities that I developed. It can be implemented in all Austrian federal states. According to this model, every municipality should be obliged by law to stipulate legally binding minimum building densities – i.e. lower bounds of the permissible building density – appropriate to the respective location for all land zoned for residential use. With few exceptions, these minimum building densities should have to be observed as soon as a new building is erected or an existing building is modified. As a result, especially detached single-family houses in their conventional – particularly land consuming – manner should eventually become phased out.

B6O is a possible candidate of superhard materials with a hardness of 45 GPa measured on single crystals. Up to now, densification of these materials was only possible at high pressure. However, recently it was found that Al2O3 can be utilized as an effective sintering additive, similar to the addition of Y2O3/Al2O3 that was used in this work. The densification behavior of the material as a function of applied pressure, its microstructure evolution, and the resulting mechanical properties were investigated. A strong dependence of the densification with increasing pressure was found. The material revealed characteristic triple junctions filled with amorphous residue composed of B2O3, Al2O3, and Y2O3, while no amorphous grain-boundary films were observed along internal interfaces. Mechanical testing revealed on average a hardness of 33 GPa, a fracture toughness of 4 MPa. m(1/2), and a strength value of 520 MPa.

The densification and phase formation of liquid phase sintered silicon carbide (LPSSiC) with 10wt.% additives were investigated. The ratio of the Al(sub 2)O(sub 3)/Y(sub 2)O(sub 3)-additives was changed between 4:1 and 1:2. Densification was carried out by hot pressing and gas pressure sintering. The different densification routes result in different major grain boundary phases-aluminates in gas pressure sintered materials and silicates in hot pressed samples. Thermodynamic calculations were carried out to determine the amount of liquid phase during densification and for the interpretation of the results.

The structure and the electrical properties of porous and dense liquid-phase sintered silicon carbide ceramics (LPS-SiC), containing yttria and alumina additives, have been studied. The electrical resistance of LPS-SiC-materials varies in a wide range. This paper is focused on the influence of porosity on the electrical resistance of the sintered SiC. The porosity was controlled by the SiC grain size. Porous LPS-SiC materials were found to have substantially lower electrical resistance in comparison to dense materials of the same type. The structure of the materials was investigated by XRD and FESEM. The porous materials consist of large grains due to the coarser starting powders in comparison to the dense materials. This results in a reduction of the dissolved and re-precipitated fraction of the SiC during sintering. Using the in-lens SEM mode, the high conductivity of the formed rims of the SiC grains could be shown. These observations reveal that the rim volume of dense LPS-SiC is much more extended than the rims of porous materials showing the higher conductivity.