Environmentally Friendly Engineering and Three-Dimensional Printing of TiO₂ Hierarchical Mesoporous Cellular Architectures

Abstract

Three-dimensional (3D) printing of hierarchically ordered cellular materials with tunable microstructures is a major challenge from both synthesis and scalable manufacturing perspectives. A simple, environmentally friendly, and scalable concept to realize morphologically and microstructurally engineered cellular ceramics is herein demonstrated by combining direct foam writing with colloidal processing. These cellular structures are widely applicable across multiple technological fields including energy harvesting, waste management/water purification, and biomedicine. Our concept marries sacrificial templating with direct foaming to synthesize multiscale porous TiO2 foams that can be 3D printed into planar, free-standing, and spanning hierarchical structures. The latter being reported for the first time. We show how by varying the foam-inks’ composition and frothing conditions, the rheological properties and foam configurations (i.e., open- or closed-cell) are tuned. Furthermore, our printing studies indicate a synergy between intermediate extrusion pressures and low speeds for realizing spanning features. Additionally, the dimensional changes associated with the postprocessing of the different foam configurations are discussed. We investigate the effects of the foams’ composition on their microstructure and surface area properties. Additionally, the foams’ photocatalytic performance is correlated with their microstructure, improving for open-cell architectures. The proposed synthesis and scalable manufacturing method can be extended to fabricate similar structures from alternative ceramic foam systems, where control of the porosity and surface properties is crucial, demonstrating the great potential of our synthesis approach.

3D Printing of Hierarchical Porous Silica and α‐Quartz

“…The need to deliberately fabricate and design silica‐based materials has been evident for decades and gained further interest in recent years with the emergence of approaches to create tailor‐made structures on the nanometer scale . The permanently growing 3D printing community has also put effort in the deliberate processing of SiO 2 and researchers have already achieved some breakthroughs such as the preparation of printable silica inks, or the 3D printing of ceramic components like porous scaffolds, and very recently transparent glass . However, there is still a long way to go in the extension of design possibilities, solvent‐free processing, etc., and therefore in the exploration of novel synthesis routes.…”

Engineered Inks for Environment-Friendly Additive Manufacturing of Hierarchical Microstructures

“…At this point, it becomes necessary to highlight the structural role of the oil phase which prevents the structure from cracking upon drying. However, during sintering, its cracking behavior will depend on additional aspects such as open-or closedcell configurations, and relative L:S:O and TALH:TiO2 ratios [276]; as discussed in the previous chapter. Both XG-stabilized inks, (Ag-decorated and baseline) result in similar film morphologies as observed from Figure 61 and Figure 62.…”

The Nakahara Effect and Its Influence On Solution-Based 3D Printed Films

“…The determined pattern was accomplished by capitalizing on previously developed processing maps and direct writing films using a range of parameters, such as pressure and speed. 3 Films were dried using different processes to determine potential contributions of deposition method and drying. The primary objective was studied by comparing mechanical properties of films fabricated using methods of direct writing or doctor blading and dried using various drying techniques.…”

“…1,2 It has already been established that ceramic based inks can be directly written into TiO2 films, specifically. 3 One area of interest is to understand the most optimal and efficient way of depositing TiO2 films on a larger scale. In this research, the direct writing and mechanical behavior of multiphase TiO2-based inks were investigated, by controlling their printing parameters, such as pressure and speed.…”

“…The approach used in ink fabrication is an environmentally friendly process: it uses abundant, water-compatible, nontoxic material precursors. 3 The TiO2 inks consist of an aqueous phase consisting of TiO 2 , Titanium(IV) bis ammonium lactato di-hydroxide (TALH) and deionized water. The TiO2 inks were mixed with Xanthan gum in order to enable advantageous printing.…”