The master thesis deals mainly with the optimization of machining of ceramic semi-finished products from ZrO2 and Al2O3. The first part with literary research, which describes the steps of the technology of forming ceramic bodies, especially the gelcasting method. The thesis describes possibilities of milling of ceramic materials using CNC technology. The thesis describes the dependence of acquired roughness on bodies and used machining strategies. The best roughness parameters on ZrO2 samples were obtained after they were calcined at 900 ° C, while the lowest roughness was obtained on the samples in the unprotected state for the Al2O3 samples. Samples machined with a spherical milling cutter showed surface roughness Ra = 1 m for ZrO2 and Ra = 1.3 m for Al2O3. It also describes the possibility of machining sharp-edged shapes and fine details where the best results are achieved on ZrO2 samples engraved at 900 and 1100 °C. Tool wear was particularly important when machining samples of Al2O3 ignited at temperatures above 800 °C.

Ce travail se place dans le cadre du traitement-recyclage des combustibles usés pour des réacteurs nucléaires de Génération IV. Ce travail s’est focalisé sur l’étape de mise en forme du combustible en étudiant plus spécifiquement les potentialités du procédé de coulage-gélification. Cette étude a porté dans un premier temps sur un simulant non radioactif de l’oxyde mixte (U,Pu)O2, à savoir l’oxyde de cérium CeO2. Des formulations de suspensions ont été identifiés permettant leur gélification dans des moules non poreux. Ce processus de gélification s’appuie sur des réactions de polymérisation. L’étude du comportement thermique des crus a permis de définir des traitements conduisant à l’élimination complète des auxiliaires organiques et à la densification quasi-complète des crus. L’optimisation du procédé de coulage-gélification a permis d’élaborer des céramiques de CeO2 de forme annulaire répondant au cahier des charges des futurs combustibles.L’ensemble du procédé de coulage-gélification a pu être transposé à une poudre d’oxyde mixte (U,Ce)O2 synthétisée par co-précipitation oxalique. Pour cela, les caractéristiques spécifiques de cette poudre ont été prises en compte et ont nécessité le recours à une étape de supplémentaire de désagglomération. / This work falls within the framework of the reprocessing-recycling of 4th Generation nuclear used fuels. This work was focused on nuclear fuel shaping process by studying more specifically the potential of gelcasting process. This study first examined a non-radioactive surrogate of mixed oxide (U,Pu)O2, namely the cerium oxide CeO2. Suspension formulations have been identified allowing gelation in non-porous molds. This gelling process is based on polymerization reactions. The study of green compacts thermal behavior has allowed to define treatments leading to the complete elimination of every organic auxiliaries and to the green compacts densification. Every step of the gelcasting process was optimized to elaborate annular shape CeO2 ceramics meeting the specification.The whole gelcasting process has been transposed to a mixed oxide (U,Ce)O2 powder synthesized by oxalic co-precipitation. To this end, powder characteristics have been taken in consideration and have required an additional deagglomeration step.

In the diploma thesis, overviews of the existing literature focused on the gelcasting method and based on the findings were prepared aqueous slurries of zirconium oxide for gelcasting method. These suspensions were examined for the influence of the content ceramics powder, type and content of dispersants and volume of initiator on viscosity of aqueous suspensions and process of polymerization. Optimum ceramic suspension had 45 vol.% of ceramic powder which was stabilized by 0,5 weight % of dispersant Dolapix CE 64. Polymerization running at room temperature was initiated by 0,175 weight % of ammonium persufate without accelerator. Microstructure of prepared ceramic blanks and sintered bodies was compared with body prepared by isostatic pressing. For the machining tests were prepared blanks in disc-shaped.