3D printing of dense and porous TiO2 structures

Direct ink writing of hierarchical porous ultra‐high temperature ceramics (ZrB2)

“…These results compare favorably with the strength-to-density ratio of 3D printed hierarchical porous oxide ceramics reported in the literature. 12,16,17,20 An analytical mechanics model has been developed to predict the elastic moduli of the structures as a function of the print architecture and modulus of the filaments which depends on the porosity within. The materials have the potential for applications in high-temperature aerospace applications as insulation, for example, between extremely hightemperature combustors and the structural airframe typically produced from polymer matrix composites or light metals.…”

“…The formulations are based on similar formulations developed for 3D printing multi-scale porous alumina ceramics. 20 Aqueous ceramic suspensions were initially prepared with 25 vol% solids in pH 4.0 reverse osmosis water. To achieve a degree of green strength between printing and firing, 4% (by weight of ceramic powder) of a common ceramic binder, polyvinyl alcohol (Celvol ® 205S, Sekisui Specialty Chemicals Europe S.L., Tarragona Spain) was dissolved in pH 2.5 water before addition of the ceramic powder to the polymer solution.…”

“…This is the first reported Weibull analysis of 4-point bend strengths of 3D printed multiscale porous UHTCs. The bend strengths need to be converted to equivalent compressive strengths in order compare to the compressive strength results for other 3D printed hierarchical porous ceramics from Minas et al, 12 Maurath et al, 16 Weiß et al, 17 and Aleni et al 20 Ceramics are well known to be stronger in compression than in tension and bending strengths lie between these two extremes. The bend strengths were multiplied by 5 in order to convert them to equivalent compressive strengths based on comparisons between concrete compressive and bend strengths.…”

“…33,34 Figure 11 compares the equivalent compressive strength of the UHTC bars with the previously published results. 12,16,17,20 The average of the Archimedes bulk density and the geometric bulk density was used to determine the relative density of the test bars as discussed in the Density and Porosity section above. To gain further insight into what may be driving the mechanical response of these multi-scale porous structures, we have constructed a model to predict the flexural response of logpile structures combining both levels of porosity.…”

“…18 Aerosol Jet techniques were developed by Saleh et al 19 to produce 3D hierarchical structures via pointwise printing with geometric features occurring over five orders of magnitude in length scale. Aleni et al 20 have also produced TiO 2 foam inks for direct ink writing which produced porous ceramics with high strength-to-density ratio. Only recently has printing of UHTCs (ultra-high temperature ceramics) been demonstrated 21 although no attempt was made to produce hierarchical porous structures.…”