The possibility of using diatomaceous earth as Si precursor for low temperature synthesis of non-oxide powders by carbothermal reduction-nitridation was studied. It was found that carbonitriding ...reactions produce phases of the Si-Al-O-N system. Already at 1300 °C, nanosized non-oxide powders were obtained. The comparatively low reaction temperatures is attributred to the nano-porous nature of the raw material. The evolution of crystalline phases proceeded via many intermediate stages. The powders were characterized by X-ray and SEM investigations. The results showed that diatomaceous earth can be a very effective source for obtaining non-oxide powders.
The objective of this work was to investigate the effect of two different sintering additives (CeO2 and Y2O3 + Al2O3), sintering time and amount of β-Si3N4 seeds on the densification, mechanical ...properties and microstructure of self-reinforced Si3N4 based composites obtained by pressureless sintering. Preparation of β-Si3N4 seeds, also obtained by a pressureless sintering procedure, is described. Samples without seeds were prepared for comparison. The results imply that self-reinforced silicon nitride based composites with densities close to the theoretical values and with fracture toughness of 9.3MPa m1/2 can be obtained using a presureless sintering procedure.
Ontology development for land administration Bošković, D; Ristić, A; Govedarica, M ...
IEEE 8th International Symposium on Intelligent Systems and Informatics,
2010-Sept.
Conference Proceeding
This paper presents ontology architecture for the land administration domain, which should provide shared vocabulary for semantic interoperability between cadastral systems. This ontology is based on ...general geospatial ontology which describes generic concepts from geospatial domain such as geometry and topology and is in correspondence with geospatial standards: ISO 19100 series and OGC. Land administration ontology is based on the Land Administration Domain Model specified in ISO 19152 standard which is extended with the concepts from the Serbian national cadastre.
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