Direct 3D Printing of Silica Doped Transparent Magnesium Aluminate Spinel Ceramics

Abstract

Transparent magnesium aluminate spinel ceramics were additively manufactured via a laser direct deposition method in this study. With a minimum porosity of 0.3% achieved, highly transparent spinel samples with the highest total optical transmittance of 82% at a wavelength of 632.8 nm, were obtained by a 3D printing approach. However, cracking was found to be a major issue affecting printed spinel samples. To control prevalent cracking, the effect of silica dopants was investigated. Increased silica dopants reduced average total crack length by up to 79% and average crack density by up to 71%. However, a high dopant level limited optical transmission, attributed to increased porosity and formation of secondary phase. Further investigation found that with decreased average fracture toughness, from 2.4 MPa·m1/2 to 1.9 MPa·m1/2, the obvious reduction in crack formation after doping was related to decreased grain size and introduction of softer secondary phase during deposition. The study demonstrated the feasibility of the proposed laser direct deposition method in directly fabricating transparent spinel ceramics while dopants showed potentials in addressing cracking issues.

Microstructure and mechanical properties of melt-grown alumina-mullite/glass composites fabricated by directed laser deposition

“…This technology uses a high-energy laser beam to melt powder materials to form components on a substrate, enabling the rapid preparation of near net size complex three-dimensional components. It has the advantages of simple process, short cycle, and low cost, and has received continuous attention in the preparation of melt-grown oxide ceramic materials [26][27][28][29]. For instance, Balla et al [30] used this method to prepare crack-free alumina ceramics.…”

Injection Molding of Magnesium Aluminate Spinel Nanocomposites for High‐Throughput Manufacturing of Transparent Ceramics

“…The transparent MAS ceramic shows a high transmission close to the theoretical maximum with up to 84 % transmission at 1000 nm (theoretical maximum at 1000 nm = 87.3 %) similar to previous reports on transparent MAS ceramics. [ 16 , 17 , 28 , 33 , 37 , 38 ] A slight absorption can be observed in the upper NIR region reducing the transmission by 10% at most. This absorption may be caused by Fe 2+ impurities, probably due to non‐hardened steels employed in the injection molding process.…”

“…[ 16 ] Further, direct 3D printing of transparent MAS has been shown using a laser deposition method inspired by the Verneuil method, which, however, suffers from prevalent cracking. [ 17 ] However, due to the layer‐based nature of 3D printing the printed components are inherently rough and excessive post‐processing is necessary for the fabrication of optical components. While these methods enable 3D structuring of transparent MAS, these processes are not suited for mass‐market manufacturing, which can only be achieved by high‐throughput manufacturing methods such as injection molding.…”

High-resolution structuring of transparent spinel ceramics

“…[6][7][8] Recently, methods for fabricating transparent MAS ceramics using 3D printing were shown. [9,10] Direct 3D printing by a laser deposition method as well as stereolithography of a liquid nanocomposite were demonstrated. [9,10] However, 3D printing by laser direct deposition resulted in parts that showed prevalent cracking while stereolithography printed parts showed a layer-by-layer structure, making is unsuitable for optical surfaces.…”