An alternative method for the 3D printing of ceramic micro lattices has been created by a group of U.S. researchers. These lattices contain far fewer flaws than those manufactured by means of conventional sintering methods, which makes them a lot stronger and more durable. Potential applications for this process range from items as small as micro-electromechanical systems up to jet engines or even space shuttles if need be.
Some Challenges Experienced
While ceramics are usually quite strong, they can be brittle, which means that they cannot be cast or machined that easily. In most cases, they are sintered by means of fusing grains of powder at excessively high temperatures, which can introduce microscopic flaws. These flaws then crack when the ceramic material is stressed in any way, resulting in the actual strength of the ceramics being far lower than its actual intrinsic strength. Materials scientist, Tobias Schaedler and his colleagues at HRL Laboratories, made use of ‘preceramic polymers,’ which, when heated, pyrolized into ceramic materials.
A more homogenous substance with fewer defects can be produced when the polymers in questions are deposited as high-purity liquid substances. Schaedler and his team made use of a combination of silazne and siloxane, which, when put through the process of pyrolysis, produced a silicon oxycarbide ceramic. They then used UV light to crosslink the polymer in the right areas to form the desired object.
Various 3D Printing Methods Used
The team used two 3D printing methods during this process. Although stereo lithography can create many shapes by constructing the object in question in a series of 2D slices, this process is slow, and the rough edges it produces can weaken the object. Smooth-edged objects can be made quicker by using self-propagating photopolymer waveguide technology. This involves irradiating the polymer through a single mask at the top. As the light passes through the object and polymerizes it, the polymer forms a UV waveguide that focuses the light deeper inside the project. After washing the un-polymerized resin away, the remaining structure can be transformed in a ceramic one by firing it.
Suitable for Micro Latticed Projects
Unfortunately, this method cannot produce thick ceramic objects, as they tend to crack when fired. However, it does enable precisely structured micro lattices with extremely low densities to be formed. These can then be designed in such a way that when the material is bent, the individual struts wither compress or stretch, rendering them far stronger than randomly structured ceramic foams. Schaedler stated, “Any material is stronger in tension and compression than in bending.”
Rishi Raj from the University of Colorado, whose own group recently unveiled a method for polymer-derived ceramic manufacture as well, described the work as ‘quite significant, maybe very significant.’ Gian Domenico Sorarù from the University of Trento, Italy, mentioned that the lack of insulation could be a problem. “But maybe that is not the main task for these materials. I think applications are in the field of catalyst support, filters and burners,” he said.