Over the past decades, ceramics have attracted much interest for their superior properties, including hardness, durability, and stability in extreme environments. They meet fabrication needs in various fields ranging from transportation industry (e.g., diesel engines) to the energy sector (e.g., nuclear) but also environment, defense, aerospace, and in the medical sector (e.g., ceramic thermal barrier coatings, filters, lightweight space mirrors, hip or knee implants). [1][2][3][4][5][6] However, the fabrication of complex ceramic parts remains very challenging. Mainly because of their hardness and brittleness, conventional manufacturing processes, such as machining or molding, are limited to simple object geometries as well as being costly and time-consuming. Additive manufacturing (AM) represents an attractive alternative. Not only does it offer more flexibility in terms of architecture and significantly reduce material waste but also it leads to cost-effective production in a shorter time. In the liquid-based AM technologies being used for the fabrication of ceramics, the process starts with a liquid preceramic polymer (PCP) that is first solidified into a 3D object: the so-called green body. The latter is then transformed into a ceramic material, generally denoted as polymer-derived ceramic (PDC), through a pyrolysis step. [7] Initially, PCP resins were processed or shaped using conventional polymer-forming techniques such as injection molding or extrusion. Later, it was demonstrated that by adding a photoinitiator to the liquid precursor, the solid green body can be formed by exposure to UV radiation. [8] Through photopolymerization, laser-based stereolithography (SLA) has enabled the fabrication of PCP components with high resolution and a good surface quality. [9] It consists of scanning a laser beam on the photosensitive PCP resin and selectively hardening the material, building the 3D green body
Ceramics are highly technical materials with properties of interest for multiple industries. Precisely because of their high chemical, thermal, and mechanical resistance, ceramics are difficult to mold into complex shapes. A possibility to make convoluted ceramic parts is to use preceramic polymers (PCP) in liquid form. The PCP resin is first solidified in a desired geometry and then transformed into ceramic compounds through a pyrolysis step that preserves the shape. Lightbased additive manufacturing (AM) is a promising route to achieve solidification of the PCP resin. Different approaches, such as stereolithography, have already been proposed but they all rely on a layer-by-layer printing process which sets limitations on the printing speed and object geometry. Here, we report on the fabrication of complex 3D centimeter-scale ceramic parts by using tomographic volumetric printing which is fast, high resolution and offers a lot of freedom in terms of geometrical design compared to state-of-the-art AM techniques. First, we formulated a photosensitive preceramic resin that was solidified by projecting light patterns from multiple angles. Then, the obtained 3D printed parts were converted into ceramics by pyrolyzing them in a furnace. We demonstrate the strength of this approach through the fabrication of dense microcomponents exhibiting overhangs and hollow geometries without the need of supporting structures, and characterize their resistance to high heat and harsh chemical treatments.
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