Abstract: A refractory ceramic material possessing a solidus temperature between 2500° C. and 2800° C., having a compactness greater than 85%, and a microstructure such that the material is composite of: (a) hafnium dioxide HfO2 grains having a monoclinic structure (1); (b) hafnium dioxide HfO2 grains having a cubic structure (2) which is stabilized by yttrium oxide Y2O3, the yttrium oxide Y2O3 representing 0.5 mol % to 8 mol % relative to the total number of moles of hafnium dioxide HfO2; (c) closed pores (3); (d) non-interconnected open pores. The process of manufacturing the material and a structural part incorporating the material are also set forth.

Abstract: A powder metallurgy process for the manufacture of powders of a refractory ceramic material, comprising the consecutive steps of: (i) obtaining a dry mixture of a hafnium dioxide HfO2 powder and an yttrium oxide Y2O3 powder; (ii) step of granulation by pelletization of the dry mixture under stirring in order to obtain a granulated mixture, this granulation step comprising the spraying, into the dry mixture, of an aqueous solution comprising polyvinyl alcohol (PVA) and polyethylene glycol (PEG); (iii) drying of the granulated mixture; (iv) filling of a mold with said granulated mixture; (v) isostatical or semi-isostatical pressing of the granulated mixture in order to obtain a compact mixture; (vi) sintering of the compact mixture in order to obtain a refractory ceramic material at a solidus temperature in the range between 2500° C. and 2800° C.

Abstract: A powder metallurgy process for the manufacture of powders of a refractory ceramic material, comprising the consecutive steps of: (i) obtaining a dry mixture of a hafnium dioxide HfO2 powder and an yttrium oxide Y2O3 powder; (ii) step of granulation by pelletization of the dry mixture under stirring in order to obtain a granulated mixture, this granulation step comprising the spraying, into the dry mixture, of an aqueous solution comprising polyvinyl alcohol (PVA) and polyethylene glycol (PEG); (iii) drying of the granulated mixture; (iv) filling of a mold with said granulated mixture; (v) isostatical or semi-isostatical pressing of the granulated mixture in order to obtain a compact mixture; (vi) sintering of the compact mixture in order to obtain a refractory ceramic material at a solidus temperature in the range between 2500° C. and 2800° C.

Abstract: A refractory ceramic material possessing a solidus temperature between 2500° C. and 2800° C., having a compactness greater than 85%, and a microstructure such that the material is composite and comprises: hafnium dioxide HfO2 grains having a monoclinic structure (1); hafnium dioxide HfO2 grains having a cubic structure (2) which is stabilized by yttrium oxide Y2O3, the yttrium oxide Y2O3 representing 0.5 mol % to 8 mol % relative to the total number of moles of hafnium dioxide HfO2; closed pores (3); non-interconnected open pores. The invention also relates to the process of manufacturing said material and a structural part incorporating said material.

Abstract: The invention relates to a process for thermal etching under oxidizing conditions of a ceramic, more particularly with the aim of revealing its grain boundaries and for the study of its granular microstructure. The invention applies to technical and nuclear ceramics and in particular UO2 and to (U, Pu) O2 mixtures. The thermal etching is performed in a furnace or kiln under a controlled atmosphere constituted by an oxidizing gas supplying a chemical oxygen potential of −75 to −125 kJ/mole and comprises the following successive stages: rapid rise in the temperature of the furnace to a rate of 900 to 1500° C./h from the initial temperature to a temperature plateau, maintaining the temperature at said plateau at a value of 1250 to 1450° C. for between 30 and 15 minutes, lowering the temperature to the final temperature.