Description du sujet de thèse

Robocasting is a relatively simple and environmentally friendly 3D printing process that allows for the printing of a wide variety of ceramic powders in the form of aqueous suspensions using a gas-pressure extrusion process. The main advantage of this method over other more precise 3D printing technologies such as stereolithography is the ability to drastically reduce printing times. The technological challenges of robocasting lie in the precision of printing and in the control of dispersion and rheological properties of ceramic suspensions. The objective of this PhD is to 3D print et sinter ultra-refractories diboride ceramics. The PhD will be organized as follows: the student will become familiar with the techniques of preparation, printing, and characterization of suspensions from ceramic benchmark materials such as alumina and zirconia. These ceramics will allow starting from relatively well-known suspensions for zirconia and alumina. Once the printing and all stages of preparation are mastered, the student will focus on printing a suspension of an ultra-refractory composite, Si3N4, with the following additives: Al2O3 and Y2O3, which can be produced by liquid-phase sintering under gas pressure approaches, and ZrB2/B4C, which can be produced at 2000°C. These ceramics have excellent mechanical properties. Printing complex parts with these ceramics represents a major challenge for aerospace and space applications. In the context of the "ULTRAFAB" project, a gas-pressure dilatometer capable of studying sintering at these very high temperature ranges will be installed during the first year of the PhD. The printed parts can be sintered in an SPS configuration without pressure, and for larger parts with the company SOLCERA.

Contexte de travail

The development of high-performance ceramics and the new 3D printing technics is on the verge to allow the rapid prototyping of high temperature materials like ultra-refractories. Today rapid prototyping is still very limited and restrained to mainly oxide ceramics that can be sintered easily. There is a need to develop printable refractories suspensions that can be sintered at high temperature to allow today prototyping method to reach the stage of ultra-high temperature materials.

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